diff --git a/lib/assertion.js b/lib/assertion.js
index 7a6b04d..a342a42 100644
--- a/lib/assertion.js
+++ b/lib/assertion.js
@@ -170,6 +170,8 @@ Assertion.add = function(name, func) {
     value: function() {
       var context = new Assertion(this.obj, this, name);
       context.anyOne = this.anyOne;
+      context.onlyThis = this.onlyThis;
+      // hack
       context.light = true;
 
       try {
@@ -190,6 +192,7 @@ Assertion.add = function(name, func) {
 
           // positive fail
           context.negate = false;
+          // hack
           context.light = false;
           context.fail();
         }
@@ -201,6 +204,7 @@ Assertion.add = function(name, func) {
       if (this.negate) {
         context.negate = true; // because .fail will set negate
         context.params.details = 'false negative fail';
+        // hack
         context.light = false;
         context.fail();
       }
@@ -306,3 +310,16 @@ Assertion.addChain('not', function() {
 Assertion.addChain('any', function() {
   this.anyOne = true;
 });
+
+
+/**
+ * Only modifier - currently used with .keys to check if object contains only exactly this .keys
+ *
+ * @name only
+ * @property
+ * @memberOf Assertion
+ * @category assertion
+ */
+Assertion.addChain('only', function() {
+  this.onlyThis = true;
+});
diff --git a/lib/ext/property.js b/lib/ext/property.js
index 365f3d5..8aab2e7 100644
--- a/lib/ext/property.js
+++ b/lib/ext/property.js
@@ -55,6 +55,7 @@ export default function(should, Assertion) {
 
   /**
    * Asserts given object has enumerable property with optionally value. **On success it change given object to be value of property**.
+   * **Deprecated**. Use .keys
    *
    * @name enumerable
    * @memberOf Assertion
@@ -80,7 +81,8 @@ export default function(should, Assertion) {
   });
 
   /**
-   * Asserts given object has enumerable properties
+   * Asserts given object has enumerable properties.
+   * **Deprecated**. Use .keys
    *
    * @name enumerables
    * @memberOf Assertion
@@ -289,6 +291,8 @@ export default function(should, Assertion) {
    * ({ a: 10 }).should.have.keys('a');
    * ({ a: 10, b: 20 }).should.have.keys('a', 'b');
    * (new Map([[1, 2]])).should.have.key(1);
+   *
+   * json.should.have.only.keys('type', 'version')
    */
   Assertion.add('keys', function(keys) {
     keys = aSlice.call(arguments);
@@ -300,7 +304,7 @@ export default function(should, Assertion) {
       return !hasKey(obj, key);
     });
 
-    var verb = 'to have ' + (keys.length === 1 ? 'key ' : 'keys ');
+    var verb = 'to have ' + (this.onlyThis ? 'only ': '') + (keys.length === 1 ? 'key ' : 'keys ');
 
     this.params = {operator: verb + keys.join(', ')};
 
@@ -309,6 +313,10 @@ export default function(should, Assertion) {
     }
 
     this.assert(missingKeys.length === 0);
+
+    if (this.onlyThis) {
+      obj.should.have.size(keys.length);
+    }
   });
 
 
@@ -363,17 +371,11 @@ export default function(should, Assertion) {
    * ({ a: {b: 10}}).should.have.propertyByPath('a', 'b').eql(10);
    */
   Assertion.add('propertyByPath', function(properties) {
-    if (arguments.length > 1) {
-      properties = aSlice.call(arguments);
-    } else if (arguments.length === 1 && typeof properties == 'string') {
-      properties = [properties];
-    } else if (arguments.length === 0) {
-      properties = [];
-    }
+    properties = aSlice.call(arguments);
 
     var allProps = properties.map(formatProp);
 
-    properties = properties.map(String);
+    properties = properties.map(convertPropertyName);
 
     var obj = should(Object(this.obj));
 
diff --git a/lib/util.js b/lib/util.js
index 9c525ca..85822cd 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -12,6 +12,7 @@ export function isWrapperType(obj) {
     obj instanceof Boolean;
 }
 
+// XXX make it more strict: numbers, strings, symbols - and nothing else
 export function convertPropertyName(name) {
   return (typeof name === 'symbol') ? name : String(name);
 }
diff --git a/test/ext/property.test.js b/test/ext/property.test.js
index 09aeb41..9e6a0f0 100644
--- a/test/ext/property.test.js
+++ b/test/ext/property.test.js
@@ -179,6 +179,10 @@ describe('property', function() {
 
     ({ '1': 'cancelled', '3': 'deleted' }).should.have.keys(1, 3);
 
+    ({ a: 10, b: 11 }).should.only.have.keys('a', 'b');
+
+    ({ a: 10, b: 11, c: 999 }).should.not.only.have.keys('a', 'b');
+
     err(function() {
       ({ foo: 1 }).should.have.keys('bar');
     }, "expected Object { foo: 1 } to have key bar\n\tmissing keys: bar");