diff --git a/.travis.yml b/.travis.yml
index 1457ce05b..b71e6844e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,6 +4,11 @@ node_js:
   - "4.0.0"
   - "0.12"
   - "0.10"
+before_install:
+  - mkdir travis-phantomjs
+  - wget https://bitbucket.org/ariya/phantomjs/downloads/phantomjs-2.1.1-linux-x86_64.tar.bz2 -O $PWD/travis-phantomjs/phantomjs-2.1.1-linux-x86_64.tar.bz2
+  - tar -xvf $PWD/travis-phantomjs/phantomjs-2.1.1-linux-x86_64.tar.bz2 -C $PWD/travis-phantomjs
+  - export PATH=$PWD/travis-phantomjs/phantomjs-2.1.1-linux-x86_64/bin:$PATH
 install:
   - npm install -g grunt-cli
   - npm install
diff --git a/lib/less/parser/parser.js b/lib/less/parser/parser.js
index 008db4a8d..b66fc5f3f 100644
--- a/lib/less/parser/parser.js
+++ b/lib/less/parser/parser.js
@@ -261,7 +261,7 @@ var Parser = function Parser(context, imports, fileInfo) {
                     }
 
                     node = mixin.definition() || this.rule() || this.ruleset() ||
-                        mixin.call() || this.rulesetCall() || this.directive();
+                        mixin.call() || this.rulesetCall() || this.entities.call() || this.directive();
                     if (node) {
                         root.push(node);
                     } else {
@@ -370,19 +370,51 @@ var Parser = function Parser(context, imports, fileInfo) {
                     return new(tree.Call)(name, args, index, fileInfo);
                 },
                 arguments: function () {
-                    var args = [], arg;
+                    var argsSemiColon = [], argsComma = [],
+                        expressions = [],
+                        isSemiColonSeparated, value, arg;
+
+                    parserInput.save();
 
                     while (true) {
-                        arg = this.assignment() || parsers.expression();
+
+                        arg = parsers.detachedRuleset() || this.assignment() || parsers.expression();
+
                         if (!arg) {
                             break;
                         }
-                        args.push(arg);
-                        if (! parserInput.$char(',')) {
-                            break;
+
+                        value = arg;
+
+                        if (arg.value && arg.value.length == 1) {
+                            value = arg.value[0];
+                        }
+
+                        if (value) {
+                            expressions.push(value);
+                        }
+
+                        argsComma.push(value);
+
+                        if (parserInput.$char(',')) {
+                            continue;
+                        }
+
+                        if (parserInput.$char(';') || isSemiColonSeparated) {
+
+                            isSemiColonSeparated = true;
+
+                            if (expressions.length > 1) {
+                                value = new(tree.Value)(expressions);
+                            }
+                            argsSemiColon.push(value);
+
+                            expressions = [];
                         }
                     }
-                    return args;
+
+                    parserInput.forget();
+                    return isSemiColonSeparated ? argsSemiColon : argsComma;
                 },
                 literal: function () {
                     return this.dimension() ||
diff --git a/lib/less/tree/anonymous.js b/lib/less/tree/anonymous.js
index d3da585ad..ec4f31304 100644
--- a/lib/less/tree/anonymous.js
+++ b/lib/less/tree/anonymous.js
@@ -6,7 +6,7 @@ var Anonymous = function (value, index, currentFileInfo, mapLines, rulesetLike,
     this.mapLines = mapLines;
     this.currentFileInfo = currentFileInfo;
     this.rulesetLike = (typeof rulesetLike === 'undefined') ? false : rulesetLike;
-
+    this.allowRoot = true;
     this.copyVisibilityInfo(visibilityInfo);
 };
 Anonymous.prototype = new Node();
diff --git a/lib/less/tree/call.js b/lib/less/tree/call.js
index 279b6fa52..12e183747 100644
--- a/lib/less/tree/call.js
+++ b/lib/less/tree/call.js
@@ -31,18 +31,21 @@ Call.prototype.eval = function (context) {
     var args = this.args.map(function (a) { return a.eval(context); }),
         result, funcCaller = new FunctionCaller(this.name, context, this.index, this.currentFileInfo);
 
-    if (funcCaller.isValid()) { // 1.
+    if (funcCaller.isValid()) {
         try {
             result = funcCaller.call(args);
-            if (result != null) {
-                return result;
-            }
         } catch (e) {
             throw { type: e.type || "Runtime",
                     message: "error evaluating function `" + this.name + "`" +
                              (e.message ? ': ' + e.message : ''),
                     index: this.index, filename: this.currentFileInfo.filename };
         }
+
+        if (result != null) {
+            result.index = this.index;
+            result.currentFileInfo = this.currentFileInfo;
+            return result;
+        }
     }
 
     return new Call(this.name, args, this.index, this.currentFileInfo);
diff --git a/lib/less/tree/comment.js b/lib/less/tree/comment.js
index 6983c6300..6566950c9 100644
--- a/lib/less/tree/comment.js
+++ b/lib/less/tree/comment.js
@@ -5,6 +5,7 @@ var Comment = function (value, isLineComment, index, currentFileInfo) {
     this.value = value;
     this.isLineComment = isLineComment;
     this.currentFileInfo = currentFileInfo;
+    this.allowRoot = true;
 };
 Comment.prototype = new Node();
 Comment.prototype.type = "Comment";
diff --git a/lib/less/tree/directive.js b/lib/less/tree/directive.js
index 3e754d435..70be82c73 100644
--- a/lib/less/tree/directive.js
+++ b/lib/less/tree/directive.js
@@ -23,6 +23,7 @@ var Directive = function (name, value, rules, index, currentFileInfo, debugInfo,
     this.debugInfo = debugInfo;
     this.isRooted = isRooted || false;
     this.copyVisibilityInfo(visibilityInfo);
+    this.allowRoot = true;
 };
 
 Directive.prototype = new Node();
diff --git a/lib/less/tree/extend.js b/lib/less/tree/extend.js
index e51604243..e91fbf77d 100644
--- a/lib/less/tree/extend.js
+++ b/lib/less/tree/extend.js
@@ -9,6 +9,7 @@ var Extend = function Extend(selector, option, index, currentFileInfo, visibilit
     this.parent_ids = [this.object_id];
     this.currentFileInfo = currentFileInfo || {};
     this.copyVisibilityInfo(visibilityInfo);
+    this.allowRoot = true;
 
     switch(option) {
         case "all":
diff --git a/lib/less/tree/import.js b/lib/less/tree/import.js
index 57be4a75f..3787b052b 100644
--- a/lib/less/tree/import.js
+++ b/lib/less/tree/import.js
@@ -23,6 +23,7 @@ var Import = function (path, features, options, index, currentFileInfo, visibili
     this.path = path;
     this.features = features;
     this.currentFileInfo = currentFileInfo;
+    this.allowRoot = true;
 
     if (this.options.less !== undefined || this.options.inline) {
         this.css = !this.options.less || this.options.inline;
diff --git a/lib/less/tree/media.js b/lib/less/tree/media.js
index 436f6f14f..0bbd23a65 100644
--- a/lib/less/tree/media.js
+++ b/lib/less/tree/media.js
@@ -15,6 +15,7 @@ var Media = function (value, features, index, currentFileInfo, visibilityInfo) {
     this.rules = [new Ruleset(selectors, value)];
     this.rules[0].allowImports = true;
     this.copyVisibilityInfo(visibilityInfo);
+    this.allowRoot = true;
 };
 Media.prototype = new Directive();
 Media.prototype.type = "Media";
diff --git a/lib/less/tree/mixin-call.js b/lib/less/tree/mixin-call.js
index 254514524..5864a0c36 100644
--- a/lib/less/tree/mixin-call.js
+++ b/lib/less/tree/mixin-call.js
@@ -9,6 +9,7 @@ var MixinCall = function (elements, args, index, currentFileInfo, important) {
     this.index = index;
     this.currentFileInfo = currentFileInfo;
     this.important = important;
+    this.allowRoot = true;
 };
 MixinCall.prototype = new Node();
 MixinCall.prototype.type = "MixinCall";
diff --git a/lib/less/tree/mixin-definition.js b/lib/less/tree/mixin-definition.js
index e02768c10..b2e3413d0 100644
--- a/lib/less/tree/mixin-definition.js
+++ b/lib/less/tree/mixin-definition.js
@@ -27,6 +27,7 @@ var Definition = function (name, params, rules, condition, variadic, frames, vis
     this.optionalParameters = optionalParameters;
     this.frames = frames;
     this.copyVisibilityInfo(visibilityInfo);
+    this.allowRoot = true;
 };
 Definition.prototype = new Ruleset();
 Definition.prototype.type = "MixinDefinition";
diff --git a/lib/less/tree/rule.js b/lib/less/tree/rule.js
index c4318a964..99d168cff 100644
--- a/lib/less/tree/rule.js
+++ b/lib/less/tree/rule.js
@@ -12,6 +12,7 @@ var Rule = function (name, value, important, merge, index, currentFileInfo, inli
     this.inline = inline || false;
     this.variable = (variable !== undefined) ? variable
         : (name.charAt && (name.charAt(0) === '@'));
+    this.allowRoot = true;
 };
 
 function evalName(context, name) {
diff --git a/lib/less/tree/ruleset-call.js b/lib/less/tree/ruleset-call.js
index 7a62c14dd..d271c8ddd 100644
--- a/lib/less/tree/ruleset-call.js
+++ b/lib/less/tree/ruleset-call.js
@@ -3,6 +3,7 @@ var Node = require("./node"),
 
 var RulesetCall = function (variable) {
     this.variable = variable;
+    this.allowRoot = true;
 };
 RulesetCall.prototype = new Node();
 RulesetCall.prototype.type = "RulesetCall";
diff --git a/lib/less/tree/ruleset.js b/lib/less/tree/ruleset.js
index 9f1917666..dcf8ae843 100644
--- a/lib/less/tree/ruleset.js
+++ b/lib/less/tree/ruleset.js
@@ -14,6 +14,7 @@ var Ruleset = function (selectors, rules, strictImports, visibilityInfo) {
     this._lookups = {};
     this.strictImports = strictImports;
     this.copyVisibilityInfo(visibilityInfo);
+    this.allowRoot = true;
 };
 Ruleset.prototype = new Node();
 Ruleset.prototype.type = "Ruleset";
diff --git a/lib/less/visitors/to-css-visitor.js b/lib/less/visitors/to-css-visitor.js
index cc90cdd88..9dc755f98 100644
--- a/lib/less/visitors/to-css-visitor.js
+++ b/lib/less/visitors/to-css-visitor.js
@@ -199,13 +199,24 @@ ToCSSVisitor.prototype = {
         return directiveNode;
     },
 
-    checkPropertiesInRoot: function(rules) {
-        var ruleNode;
+    checkValidNodes: function(rules, isRoot) {
+        if (!rules) {
+            return;
+        }
+
         for (var i = 0; i < rules.length; i++) {
-            ruleNode = rules[i];
-            if (ruleNode instanceof tree.Rule && !ruleNode.variable) {
-                throw { message: "properties must be inside selector blocks, they cannot be in the root.",
-                    index: ruleNode.index, filename: ruleNode.currentFileInfo ? ruleNode.currentFileInfo.filename : null};
+            var ruleNode = rules[i];
+            if (isRoot && ruleNode instanceof tree.Rule && !ruleNode.variable) {
+                throw { message: "Properties must be inside selector blocks. They cannot be in the root",
+                    index: ruleNode.index, filename: ruleNode.currentFileInfo && ruleNode.currentFileInfo.filename};
+            }
+            if (ruleNode instanceof tree.Call) {
+                throw { message: "Function '" + ruleNode.name + "' is undefined",
+                    index: ruleNode.index, filename: ruleNode.currentFileInfo && ruleNode.currentFileInfo.filename};
+            }
+            if (!ruleNode.allowRoot) {
+                throw { message: ruleNode.type + " node returned by a function is not valid here",
+                    index: ruleNode.index, filename: ruleNode.currentFileInfo && ruleNode.currentFileInfo.filename};
             }
         }
     },
@@ -213,9 +224,9 @@ ToCSSVisitor.prototype = {
     visitRuleset: function (rulesetNode, visitArgs) {
         //at this point rulesets are nested into each other
         var rule, rulesets = [];
-        if (rulesetNode.firstRoot) {
-            this.checkPropertiesInRoot(rulesetNode.rules);
-        }
+
+        this.checkValidNodes(rulesetNode.rules, rulesetNode.firstRoot);
+
         if (! rulesetNode.root) {
             //remove invisible paths
             this._compileRulesetPaths(rulesetNode);
diff --git a/test/css/plugin.css b/test/css/plugin.css
index b837dc63e..0b6910754 100644
--- a/test/css/plugin.css
+++ b/test/css/plugin.css
@@ -1,3 +1,4 @@
+@charset "utf-8";
 .other {
   trans: transitive;
 }
@@ -42,3 +43,7 @@
     result: local;
   }
 }
+.root {
+  prop: value;
+}
+@arbitrary value after ();
diff --git a/test/less/errors/detached-ruleset-3.txt b/test/less/errors/detached-ruleset-3.txt
index 15d281fa3..ad43ab46a 100644
--- a/test/less/errors/detached-ruleset-3.txt
+++ b/test/less/errors/detached-ruleset-3.txt
@@ -1,4 +1,4 @@
-SyntaxError: properties must be inside selector blocks, they cannot be in the root. in {path}detached-ruleset-3.less on line 2, column 3:
+SyntaxError: Properties must be inside selector blocks. They cannot be in the root in {path}detached-ruleset-3.less on line 2, column 3:
 1 @a: {
 2   b: 1;
 3 };
diff --git a/test/less/errors/functions-1.less b/test/less/errors/functions-1.less
new file mode 100644
index 000000000..f502aa276
--- /dev/null
+++ b/test/less/errors/functions-1.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-undefined();
\ No newline at end of file
diff --git a/test/less/errors/functions-1.txt b/test/less/errors/functions-1.txt
new file mode 100644
index 000000000..abeb4bda5
--- /dev/null
+++ b/test/less/errors/functions-1.txt
@@ -0,0 +1,3 @@
+SyntaxError: Function 'test-undefined' is undefined in {path}functions-1.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-undefined();
diff --git a/test/less/errors/functions-10-keyword.less b/test/less/errors/functions-10-keyword.less
new file mode 100644
index 000000000..16d0b9858
--- /dev/null
+++ b/test/less/errors/functions-10-keyword.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-keyword();
\ No newline at end of file
diff --git a/test/less/errors/functions-10-keyword.txt b/test/less/errors/functions-10-keyword.txt
new file mode 100644
index 000000000..dabe839d6
--- /dev/null
+++ b/test/less/errors/functions-10-keyword.txt
@@ -0,0 +1,3 @@
+SyntaxError: Keyword node returned by a function is not valid here in {path}functions-10-keyword.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-keyword();
diff --git a/test/less/errors/functions-11-operation.less b/test/less/errors/functions-11-operation.less
new file mode 100644
index 000000000..5695bdb91
--- /dev/null
+++ b/test/less/errors/functions-11-operation.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-operation();
\ No newline at end of file
diff --git a/test/less/errors/functions-11-operation.txt b/test/less/errors/functions-11-operation.txt
new file mode 100644
index 000000000..27287179c
--- /dev/null
+++ b/test/less/errors/functions-11-operation.txt
@@ -0,0 +1,3 @@
+SyntaxError: Operation node returned by a function is not valid here in {path}functions-11-operation.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-operation();
diff --git a/test/less/errors/functions-12-quoted.less b/test/less/errors/functions-12-quoted.less
new file mode 100644
index 000000000..d35be8710
--- /dev/null
+++ b/test/less/errors/functions-12-quoted.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-quoted();
\ No newline at end of file
diff --git a/test/less/errors/functions-12-quoted.txt b/test/less/errors/functions-12-quoted.txt
new file mode 100644
index 000000000..45c62ea64
--- /dev/null
+++ b/test/less/errors/functions-12-quoted.txt
@@ -0,0 +1,3 @@
+SyntaxError: Quoted node returned by a function is not valid here in {path}functions-12-quoted.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-quoted();
diff --git a/test/less/errors/functions-13-selector.less b/test/less/errors/functions-13-selector.less
new file mode 100644
index 000000000..2fd879c60
--- /dev/null
+++ b/test/less/errors/functions-13-selector.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-selector();
\ No newline at end of file
diff --git a/test/less/errors/functions-13-selector.txt b/test/less/errors/functions-13-selector.txt
new file mode 100644
index 000000000..2f4b097f2
--- /dev/null
+++ b/test/less/errors/functions-13-selector.txt
@@ -0,0 +1,3 @@
+SyntaxError: Selector node returned by a function is not valid here in {path}functions-13-selector.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-selector();
diff --git a/test/less/errors/functions-14-url.less b/test/less/errors/functions-14-url.less
new file mode 100644
index 000000000..bed6dabff
--- /dev/null
+++ b/test/less/errors/functions-14-url.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-url();
\ No newline at end of file
diff --git a/test/less/errors/functions-14-url.txt b/test/less/errors/functions-14-url.txt
new file mode 100644
index 000000000..aeb275cab
--- /dev/null
+++ b/test/less/errors/functions-14-url.txt
@@ -0,0 +1,3 @@
+SyntaxError: Url node returned by a function is not valid here in {path}functions-14-url.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-url();
diff --git a/test/less/errors/functions-15-value.less b/test/less/errors/functions-15-value.less
new file mode 100644
index 000000000..189ce1967
--- /dev/null
+++ b/test/less/errors/functions-15-value.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-value();
\ No newline at end of file
diff --git a/test/less/errors/functions-15-value.txt b/test/less/errors/functions-15-value.txt
new file mode 100644
index 000000000..41f6e6a17
--- /dev/null
+++ b/test/less/errors/functions-15-value.txt
@@ -0,0 +1,3 @@
+SyntaxError: Value node returned by a function is not valid here in {path}functions-15-value.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-value();
diff --git a/test/less/errors/functions-2-alpha.less b/test/less/errors/functions-2-alpha.less
new file mode 100644
index 000000000..f00da0788
--- /dev/null
+++ b/test/less/errors/functions-2-alpha.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-alpha();
\ No newline at end of file
diff --git a/test/less/errors/functions-2-alpha.txt b/test/less/errors/functions-2-alpha.txt
new file mode 100644
index 000000000..38a172731
--- /dev/null
+++ b/test/less/errors/functions-2-alpha.txt
@@ -0,0 +1,3 @@
+SyntaxError: Alpha node returned by a function is not valid here in {path}functions-2-alpha.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-alpha();
diff --git a/test/less/errors/functions-3-assignment.less b/test/less/errors/functions-3-assignment.less
new file mode 100644
index 000000000..fe7f5ade4
--- /dev/null
+++ b/test/less/errors/functions-3-assignment.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-assignment();
\ No newline at end of file
diff --git a/test/less/errors/functions-3-assignment.txt b/test/less/errors/functions-3-assignment.txt
new file mode 100644
index 000000000..35c199265
--- /dev/null
+++ b/test/less/errors/functions-3-assignment.txt
@@ -0,0 +1,3 @@
+SyntaxError: Assignment node returned by a function is not valid here in {path}functions-3-assignment.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-assignment();
diff --git a/test/less/errors/functions-4-call.less b/test/less/errors/functions-4-call.less
new file mode 100644
index 000000000..6b55c88a7
--- /dev/null
+++ b/test/less/errors/functions-4-call.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-call();
\ No newline at end of file
diff --git a/test/less/errors/functions-4-call.txt b/test/less/errors/functions-4-call.txt
new file mode 100644
index 000000000..338582d7c
--- /dev/null
+++ b/test/less/errors/functions-4-call.txt
@@ -0,0 +1,3 @@
+SyntaxError: Function 'foo' is undefined in {path}functions-4-call.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-call();
diff --git a/test/less/errors/functions-5-color-2.less b/test/less/errors/functions-5-color-2.less
new file mode 100644
index 000000000..4839416b0
--- /dev/null
+++ b/test/less/errors/functions-5-color-2.less
@@ -0,0 +1 @@
+rgba(0,0,0,0);
\ No newline at end of file
diff --git a/test/less/errors/functions-5-color-2.txt b/test/less/errors/functions-5-color-2.txt
new file mode 100644
index 000000000..8b36fd985
--- /dev/null
+++ b/test/less/errors/functions-5-color-2.txt
@@ -0,0 +1,2 @@
+SyntaxError: Color node returned by a function is not valid here in {path}functions-5-color-2.less on line 1, column 1:
+1 rgba(0,0,0,0);
diff --git a/test/less/errors/functions-5-color.less b/test/less/errors/functions-5-color.less
new file mode 100644
index 000000000..700ec5b92
--- /dev/null
+++ b/test/less/errors/functions-5-color.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-color();
\ No newline at end of file
diff --git a/test/less/errors/functions-5-color.txt b/test/less/errors/functions-5-color.txt
new file mode 100644
index 000000000..fdcd1a08a
--- /dev/null
+++ b/test/less/errors/functions-5-color.txt
@@ -0,0 +1,3 @@
+SyntaxError: Color node returned by a function is not valid here in {path}functions-5-color.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-color();
diff --git a/test/less/errors/functions-6-condition.less b/test/less/errors/functions-6-condition.less
new file mode 100644
index 000000000..db1000b83
--- /dev/null
+++ b/test/less/errors/functions-6-condition.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-condition();
\ No newline at end of file
diff --git a/test/less/errors/functions-6-condition.txt b/test/less/errors/functions-6-condition.txt
new file mode 100644
index 000000000..421bba5f5
--- /dev/null
+++ b/test/less/errors/functions-6-condition.txt
@@ -0,0 +1,3 @@
+SyntaxError: Condition node returned by a function is not valid here in {path}functions-6-condition.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-condition();
diff --git a/test/less/errors/functions-7-dimension.less b/test/less/errors/functions-7-dimension.less
new file mode 100644
index 000000000..c399d33e2
--- /dev/null
+++ b/test/less/errors/functions-7-dimension.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-dimension();
\ No newline at end of file
diff --git a/test/less/errors/functions-7-dimension.txt b/test/less/errors/functions-7-dimension.txt
new file mode 100644
index 000000000..3b1b7026c
--- /dev/null
+++ b/test/less/errors/functions-7-dimension.txt
@@ -0,0 +1,3 @@
+SyntaxError: Dimension node returned by a function is not valid here in {path}functions-7-dimension.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-dimension();
diff --git a/test/less/errors/functions-8-element.less b/test/less/errors/functions-8-element.less
new file mode 100644
index 000000000..c762aad81
--- /dev/null
+++ b/test/less/errors/functions-8-element.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-element();
\ No newline at end of file
diff --git a/test/less/errors/functions-8-element.txt b/test/less/errors/functions-8-element.txt
new file mode 100644
index 000000000..b505d9543
--- /dev/null
+++ b/test/less/errors/functions-8-element.txt
@@ -0,0 +1,3 @@
+SyntaxError: Element node returned by a function is not valid here in {path}functions-8-element.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-element();
diff --git a/test/less/errors/functions-9-expression.less b/test/less/errors/functions-9-expression.less
new file mode 100644
index 000000000..5f0bf46c4
--- /dev/null
+++ b/test/less/errors/functions-9-expression.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes";
+test-expression();
\ No newline at end of file
diff --git a/test/less/errors/functions-9-expression.txt b/test/less/errors/functions-9-expression.txt
new file mode 100644
index 000000000..224db785e
--- /dev/null
+++ b/test/less/errors/functions-9-expression.txt
@@ -0,0 +1,3 @@
+SyntaxError: Expression node returned by a function is not valid here in {path}functions-9-expression.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes";
+2 test-expression();
diff --git a/test/less/errors/property-in-root.txt b/test/less/errors/property-in-root.txt
index 04b277660..10c985344 100644
--- a/test/less/errors/property-in-root.txt
+++ b/test/less/errors/property-in-root.txt
@@ -1,4 +1,4 @@
-SyntaxError: properties must be inside selector blocks, they cannot be in the root. in {path}property-in-root.less on line 2, column 3:
+SyntaxError: Properties must be inside selector blocks. They cannot be in the root in {path}property-in-root.less on line 2, column 3:
 1 .a() {
 2   prop:1;
 3 }
diff --git a/test/less/errors/property-in-root2.txt b/test/less/errors/property-in-root2.txt
index 04b277660..10c985344 100644
--- a/test/less/errors/property-in-root2.txt
+++ b/test/less/errors/property-in-root2.txt
@@ -1,4 +1,4 @@
-SyntaxError: properties must be inside selector blocks, they cannot be in the root. in {path}property-in-root.less on line 2, column 3:
+SyntaxError: Properties must be inside selector blocks. They cannot be in the root in {path}property-in-root.less on line 2, column 3:
 1 .a() {
 2   prop:1;
 3 }
diff --git a/test/less/errors/property-in-root3.txt b/test/less/errors/property-in-root3.txt
index 68ef9454d..13a49052e 100644
--- a/test/less/errors/property-in-root3.txt
+++ b/test/less/errors/property-in-root3.txt
@@ -1,3 +1,3 @@
-SyntaxError: properties must be inside selector blocks, they cannot be in the root. in {path}property-in-root3.less on line 1, column 1:
+SyntaxError: Properties must be inside selector blocks. They cannot be in the root in {path}property-in-root3.less on line 1, column 1:
 1 prop:1;
 2 .a {
diff --git a/test/less/errors/root-func-undefined-1.less b/test/less/errors/root-func-undefined-1.less
new file mode 100644
index 000000000..e5bacda6b
--- /dev/null
+++ b/test/less/errors/root-func-undefined-1.less
@@ -0,0 +1 @@
+func();
\ No newline at end of file
diff --git a/test/less/errors/root-func-undefined-1.txt b/test/less/errors/root-func-undefined-1.txt
new file mode 100644
index 000000000..a07480e61
--- /dev/null
+++ b/test/less/errors/root-func-undefined-1.txt
@@ -0,0 +1,2 @@
+SyntaxError: Function 'func' is undefined in {path}root-func-undefined-1.less on line 1, column 1:
+1 func();
diff --git a/test/less/errors/root-func-undefined-2.less b/test/less/errors/root-func-undefined-2.less
new file mode 100644
index 000000000..ee34616e1
--- /dev/null
+++ b/test/less/errors/root-func-undefined-2.less
@@ -0,0 +1,2 @@
+@plugin "../plugin/plugin-tree-nodes.js";
+test-undefined();
\ No newline at end of file
diff --git a/test/less/errors/root-func-undefined-2.txt b/test/less/errors/root-func-undefined-2.txt
new file mode 100644
index 000000000..031385d01
--- /dev/null
+++ b/test/less/errors/root-func-undefined-2.txt
@@ -0,0 +1,3 @@
+SyntaxError: Function 'test-undefined' is undefined in {path}root-func-undefined-2.less on line 2, column 1:
+1 @plugin "../plugin/plugin-tree-nodes.js";
+2 test-undefined();
diff --git a/test/less/plugin.less b/test/less/plugin.less
index 17524a400..66775ea9f 100644
--- a/test/less/plugin.less
+++ b/test/less/plugin.less
@@ -81,5 +81,13 @@
   }
 }
 
+@plugin "./plugin/plugin-tree-nodes";
+@ruleset2: test-detached-ruleset();
+.root {
+  @ruleset2();
+}
+
+test-directive("@charset"; '"utf-8"');
+test-directive("@arbitrary"; "value after ()");
 
 
diff --git a/test/less/plugin/plugin-tree-nodes.js b/test/less/plugin/plugin-tree-nodes.js
new file mode 100644
index 000000000..442352d7f
--- /dev/null
+++ b/test/less/plugin/plugin-tree-nodes.js
@@ -0,0 +1,80 @@
+functions.addMultiple({
+
+    "test-comment": function() {
+        return new tree.Combinator(' ');
+    },
+    "test-directive": function(arg1, arg2) {
+        return new tree.Directive(arg1.value, new tree.Anonymous(arg2.value));
+    },
+    "test-extend": function() {
+        //TODO
+    },
+    "test-import": function() {
+        //TODO
+    },
+    "test-media": function() {
+        //TODO
+    },
+    "test-mixin-call": function() {
+        //TODO
+    },
+    "test-mixin-definition": function() {
+        //TODO
+    },
+    "test-ruleset-call": function() {
+        return new tree.Combinator(' ');
+    },
+    // Functions must return something. Must 'return true' if they produce no output.
+    "test-undefined": function() { },
+
+    // These cause root errors
+    "test-alpha": function() {
+        return new tree.Alpha(30);
+    },
+    "test-assignment": function() {
+        return new tree.Assignment("bird", "robin");
+    },
+    "test-attribute": function() {
+        return new tree.Attribute("foo", "=", "bar");
+    },
+    "test-call": function() {
+        return new tree.Call("foo");
+    },
+    "test-color": function() {
+        return new tree.Color([50, 50, 50]);
+    },
+    "test-condition": function() {
+        return new tree.Condition('<', new tree.Value([0]), new tree.Value([1]));
+    },
+    "test-detached-ruleset" : function() {
+        var rule = new tree.Rule('prop', new tree.Anonymous('value'));
+        return new tree.DetachedRuleset(new tree.Ruleset("", [ rule ]));
+    },
+    "test-dimension": function() {
+        return new tree.Dimension(1, 'px');
+    },
+    "test-element": function() {
+        return new tree.Element('+', 'a');
+    },
+    "test-expression": function() {
+        return new tree.Expression([1, 2, 3]);
+    },
+    "test-keyword": function() {
+        return new tree.Keyword('foo');
+    },
+    "test-operation": function() {
+        return new tree.Operation('+', [1, 2]);
+    },
+    "test-quoted": function() {
+        return new tree.Quoted('"', 'foo');
+    },
+    "test-selector": function() {
+        return new tree.Selector([new tree.Element('a')]);
+    },
+    "test-url": function() {
+        return new tree.URL('http://google.com');
+    },
+    "test-value": function() {
+        return new tree.Value([1]);
+    }
+});
\ No newline at end of file