diff --git a/spec/store_spec.js b/spec/store_spec.js
index 73cb6562..5d61902c 100644
--- a/spec/store_spec.js
+++ b/spec/store_spec.js
@@ -5,7 +5,7 @@ describe("Store", function () {
 
     it("Should pass integration test #1", function (done) {
         new Store.Store({name: 'test', overwrite: true}, function (err, store) {
-            expect(err == null);
+            expect(err).toBe(null);
             store.execute('INSERT DATA {  <http://example/book3> <http://example.com/vocab#title> <http://test.com/example> }', function (err, result) {
                 expect(err).toBe(null);
                 store.execute('SELECT * { ?s ?p ?o }', function (err, results) {
@@ -22,6 +22,32 @@ describe("Store", function () {
         });
     });
 
+    it("Should pass integration test #1a", function (done) {
+        new Store.Store({name: 'test', overwrite: true}, function (err, store) {
+            expect(err).toBe(null);
+            store.execute('SELECT * {}', function (err, results) {
+                expect(err).toBe(null);
+                expect(results.length).toBe(1);
+                store.close(function () {
+                    done();
+                });
+            });
+        });
+    });
+
+    it("Should pass integration test #1b", function (done) {
+        new Store.Store({name: 'test', overwrite: true}, function (err, store) {
+            expect(err).toBe(null);
+            store.execute('SELECT * { OPTIONAL { ?s ?p ?o } }', function (err, results) {
+                expect(err).toBe(null);
+                expect(results.length).toBe(1);
+                store.close(function () {
+                    done();
+                });
+            });
+        });
+    });
+
     it("Should pass integration test #2", function (done) {
         new Store.Store({treeOrder: 50, name: 'test', overwrite: true}, function (err, store) {
             expect(err).toBe(null);
diff --git a/src/query_engine.js b/src/query_engine.js
index e88f9d7b..ab75cfe0 100644
--- a/src/query_engine.js
+++ b/src/query_engine.js
@@ -949,7 +949,7 @@ QueryEngine.prototype.executeSelectUnit = function(projection, dataset, pattern,
         });
     } else if(pattern.kind === "EMPTY_PATTERN") {
         // as an example of this case  check DAWG test case: algebra/filter-nested-2
-        callback([]);
+        callback([{}]);
     //} else if(pattern.kind === "ZERO_OR_MORE_PATH" || pattern.kind === 'ONE_OR_MORE_PATH') {
     //    return this.executeZeroOrMorePath(pattern, dataset, env);
     } else {
@@ -1158,8 +1158,11 @@ QueryEngine.prototype.executeLEFT_JOIN = function(projection, dataset, patterns,
     var setQuery1 = patterns.lvalue;
     var setQuery2 = patterns.rvalue;
     if(setQuery1.kind === "EMPTY_PATTERN") {
-        // LEFT JOIN ( Z | X) => X
-        this.executeSelectUnit(projection, dataset, setQuery2, env, callback);
+        // LEFT JOIN ( Z | X) => X; exception: X returns no results
+        this.executeSelectUnit(projection, dataset, setQuery2, env, function (result) {
+            if (result != null && result.length > 0) callback(result);
+            else callback([{}]);
+        });
     } else {
         var set1 = null;
         var set2 = null;