diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 469ecf80c84..36f9bbb654b 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -5351,17 +5351,39 @@ module ts {
                 }
                 // Target type is type of prototype property
                 let prototypeProperty = getPropertyOfType(rightType, "prototype");
-                if (!prototypeProperty) {
-                    return type;
+                if (prototypeProperty) {
+                    let targetType = getTypeOfSymbol(prototypeProperty);
+                    if (targetType !== anyType) {
+                        // Narrow to target type if it is a subtype of current type
+                        if (isTypeSubtypeOf(targetType, type)) {
+                            return targetType;
+                        }
+                        // If current type is a union type, remove all constituents that aren't subtypes of target type
+                        if (type.flags & TypeFlags.Union) {
+                            return getUnionType(filter((<UnionType>type).types, t => isTypeSubtypeOf(t, targetType)));
+                        }
+                    }
                 }
-                let targetType = getTypeOfSymbol(prototypeProperty);
-                // Narrow to target type if it is a subtype of current type
-                if (isTypeSubtypeOf(targetType, type)) {
-                    return targetType;
+                // Target type is type of constructor signiture
+                let constructorSignitures: Signature[];
+                if (rightType.flags & TypeFlags.Interface) {
+                    constructorSignitures = (<InterfaceTypeWithDeclaredMembers>rightType).declaredConstructSignatures;
                 }
-                // If current type is a union type, remove all constituents that aren't subtypes of target type
-                if (type.flags & TypeFlags.Union) {
-                    return getUnionType(filter((<UnionType>type).types, t => isTypeSubtypeOf(t, targetType)));
+                if (rightType.flags & TypeFlags.Anonymous) {
+                    constructorSignitures = (<ResolvedType>rightType).constructSignatures;
+                }
+                if (constructorSignitures) {
+                    let constructorType = getUnionType(map(constructorSignitures, constructorSignature => {
+                        if (constructorSignature.typeParameters && constructorSignature.typeParameters.length !== 0) {
+                            // TODO convert type parameters to any or empty object types. e.g. Sample<T> -> Sample<any> or Sample<{}>.
+                        }
+                        return constructorSignature.resolvedReturnType;
+                    }));
+                    // Pickup type from union types
+                    if (type.flags & TypeFlags.Union) {
+                        return getUnionType(filter((<UnionType>type).types, t => isTypeSubtypeOf(t, constructorType)));
+                    }
+                    return constructorType;
                 }
                 return type;
             }
diff --git a/tests/baselines/reference/typeGuardsWithInstanceOfByConstructorSignature.errors.txt b/tests/baselines/reference/typeGuardsWithInstanceOfByConstructorSignature.errors.txt
new file mode 100644
index 00000000000..c7146541705
--- /dev/null
+++ b/tests/baselines/reference/typeGuardsWithInstanceOfByConstructorSignature.errors.txt
@@ -0,0 +1,111 @@
+tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOfByConstructorSignature.ts(12,10): error TS2339: Property 'bar' does not exist on type 'A'.
+tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOfByConstructorSignature.ts(32,10): error TS2339: Property 'foo' does not exist on type '{}'.
+tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOfByConstructorSignature.ts(33,10): error TS2339: Property 'foo' does not exist on type '{}'.
+tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOfByConstructorSignature.ts(34,10): error TS2339: Property 'bar' does not exist on type '{}'.
+tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOfByConstructorSignature.ts(63,10): error TS2339: Property 'bar2' does not exist on type 'C1'.
+tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOfByConstructorSignature.ts(82,10): error TS2339: Property 'bar' does not exist on type 'D'.
+
+
+==== tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOfByConstructorSignature.ts (6 errors) ====
+    interface AConstructor {
+        new (): A;
+    }
+    interface A {
+        foo: string;
+    }
+    declare var A: AConstructor;
+    
+    var obj1: A | string;
+    if (obj1 instanceof A) { // narrowed to A.
+        obj1.foo;
+        obj1.bar;
+             ~~~
+!!! error TS2339: Property 'bar' does not exist on type 'A'.
+    }
+    
+    var obj2: any;
+    if (obj2 instanceof A) { // can't type narrowing from any.
+        obj2.foo;
+        obj2.bar;
+    }
+    
+    // with generics
+    interface BConstructor {
+        new <T>(): B<T>;
+    }
+    interface B<T> {
+        foo: T;
+    }
+    declare var B: BConstructor;
+    
+    var obj3: B<string> | A;
+    if (obj3 instanceof B) { // narrowed to B<string>.
+        obj3.foo = "str";
+             ~~~
+!!! error TS2339: Property 'foo' does not exist on type '{}'.
+        obj3.foo = 1;
+             ~~~
+!!! error TS2339: Property 'foo' does not exist on type '{}'.
+        obj3.bar = "str";
+             ~~~
+!!! error TS2339: Property 'bar' does not exist on type '{}'.
+    }
+    
+    var obj4: any;
+    if (obj4 instanceof B) { // can't type narrowing from any.
+        obj4.foo = "str";
+        obj4.foo = 1;
+        obj4.bar = "str";
+    }
+    
+    // has multiple constructor signature
+    interface CConstructor {
+        new (value: string): C1;
+        new (value: number): C2;
+    }
+    interface C1 {
+        foo: string;
+        bar1: number;
+    }
+    interface C2 {
+        foo: string;
+        bar2: number;
+    }
+    declare var C: CConstructor;
+    
+    var obj5: C1 | A;
+    if (obj5 instanceof C) { // narrowed to C1.
+        obj5.foo;
+        obj5.bar1;
+        obj5.bar2;
+             ~~~~
+!!! error TS2339: Property 'bar2' does not exist on type 'C1'.
+    }
+    
+    var obj6: any;
+    if (obj6 instanceof C) { // can't type narrowing from any.
+        obj6.foo;
+        obj6.bar1;
+        obj6.bar2;
+    }
+    
+    // with object type literal
+    interface D {
+        foo: string;
+    }
+    declare var D: { new (): D; };
+    
+    var obj7: D | string;
+    if (obj7 instanceof D) { // narrowed to D.
+        obj7.foo;
+        obj7.bar;
+             ~~~
+!!! error TS2339: Property 'bar' does not exist on type 'D'.
+    }
+    
+    var obj8: any;
+    if (obj8 instanceof D) { // can't type narrowing from any.
+        obj8.foo;
+        obj8.bar;
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/typeGuardsWithInstanceOfByConstructorSignature.js b/tests/baselines/reference/typeGuardsWithInstanceOfByConstructorSignature.js
new file mode 100644
index 00000000000..c795126b0ff
--- /dev/null
+++ b/tests/baselines/reference/typeGuardsWithInstanceOfByConstructorSignature.js
@@ -0,0 +1,137 @@
+//// [typeGuardsWithInstanceOfByConstructorSignature.ts]
+interface AConstructor {
+    new (): A;
+}
+interface A {
+    foo: string;
+}
+declare var A: AConstructor;
+
+var obj1: A | string;
+if (obj1 instanceof A) { // narrowed to A.
+    obj1.foo;
+    obj1.bar;
+}
+
+var obj2: any;
+if (obj2 instanceof A) { // can't type narrowing from any.
+    obj2.foo;
+    obj2.bar;
+}
+
+// with generics
+interface BConstructor {
+    new <T>(): B<T>;
+}
+interface B<T> {
+    foo: T;
+}
+declare var B: BConstructor;
+
+var obj3: B<string> | A;
+if (obj3 instanceof B) { // narrowed to B<string>.
+    obj3.foo = "str";
+    obj3.foo = 1;
+    obj3.bar = "str";
+}
+
+var obj4: any;
+if (obj4 instanceof B) { // can't type narrowing from any.
+    obj4.foo = "str";
+    obj4.foo = 1;
+    obj4.bar = "str";
+}
+
+// has multiple constructor signature
+interface CConstructor {
+    new (value: string): C1;
+    new (value: number): C2;
+}
+interface C1 {
+    foo: string;
+    bar1: number;
+}
+interface C2 {
+    foo: string;
+    bar2: number;
+}
+declare var C: CConstructor;
+
+var obj5: C1 | A;
+if (obj5 instanceof C) { // narrowed to C1.
+    obj5.foo;
+    obj5.bar1;
+    obj5.bar2;
+}
+
+var obj6: any;
+if (obj6 instanceof C) { // can't type narrowing from any.
+    obj6.foo;
+    obj6.bar1;
+    obj6.bar2;
+}
+
+// with object type literal
+interface D {
+    foo: string;
+}
+declare var D: { new (): D; };
+
+var obj7: D | string;
+if (obj7 instanceof D) { // narrowed to D.
+    obj7.foo;
+    obj7.bar;
+}
+
+var obj8: any;
+if (obj8 instanceof D) { // can't type narrowing from any.
+    obj8.foo;
+    obj8.bar;
+}
+
+
+//// [typeGuardsWithInstanceOfByConstructorSignature.js]
+var obj1;
+if (obj1 instanceof A) {
+    obj1.foo;
+    obj1.bar;
+}
+var obj2;
+if (obj2 instanceof A) {
+    obj2.foo;
+    obj2.bar;
+}
+var obj3;
+if (obj3 instanceof B) {
+    obj3.foo = "str";
+    obj3.foo = 1;
+    obj3.bar = "str";
+}
+var obj4;
+if (obj4 instanceof B) {
+    obj4.foo = "str";
+    obj4.foo = 1;
+    obj4.bar = "str";
+}
+var obj5;
+if (obj5 instanceof C) {
+    obj5.foo;
+    obj5.bar1;
+    obj5.bar2;
+}
+var obj6;
+if (obj6 instanceof C) {
+    obj6.foo;
+    obj6.bar1;
+    obj6.bar2;
+}
+var obj7;
+if (obj7 instanceof D) {
+    obj7.foo;
+    obj7.bar;
+}
+var obj8;
+if (obj8 instanceof D) {
+    obj8.foo;
+    obj8.bar;
+}
diff --git a/tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOfByConstructorSignature.ts b/tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOfByConstructorSignature.ts
new file mode 100644
index 00000000000..b28d92e2c8e
--- /dev/null
+++ b/tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOfByConstructorSignature.ts
@@ -0,0 +1,89 @@
+interface AConstructor {
+    new (): A;
+}
+interface A {
+    foo: string;
+}
+declare var A: AConstructor;
+
+var obj1: A | string;
+if (obj1 instanceof A) { // narrowed to A.
+    obj1.foo;
+    obj1.bar;
+}
+
+var obj2: any;
+if (obj2 instanceof A) { // can't type narrowing from any.
+    obj2.foo;
+    obj2.bar;
+}
+
+// with generics
+interface BConstructor {
+    new <T>(): B<T>;
+}
+interface B<T> {
+    foo: T;
+}
+declare var B: BConstructor;
+
+var obj3: B<string> | A;
+if (obj3 instanceof B) { // narrowed to B<string>.
+    obj3.foo = "str";
+    obj3.foo = 1;
+    obj3.bar = "str";
+}
+
+var obj4: any;
+if (obj4 instanceof B) { // can't type narrowing from any.
+    obj4.foo = "str";
+    obj4.foo = 1;
+    obj4.bar = "str";
+}
+
+// has multiple constructor signature
+interface CConstructor {
+    new (value: string): C1;
+    new (value: number): C2;
+}
+interface C1 {
+    foo: string;
+    bar1: number;
+}
+interface C2 {
+    foo: string;
+    bar2: number;
+}
+declare var C: CConstructor;
+
+var obj5: C1 | A;
+if (obj5 instanceof C) { // narrowed to C1.
+    obj5.foo;
+    obj5.bar1;
+    obj5.bar2;
+}
+
+var obj6: any;
+if (obj6 instanceof C) { // can't type narrowing from any.
+    obj6.foo;
+    obj6.bar1;
+    obj6.bar2;
+}
+
+// with object type literal
+interface D {
+    foo: string;
+}
+declare var D: { new (): D; };
+
+var obj7: D | string;
+if (obj7 instanceof D) { // narrowed to D.
+    obj7.foo;
+    obj7.bar;
+}
+
+var obj8: any;
+if (obj8 instanceof D) { // can't type narrowing from any.
+    obj8.foo;
+    obj8.bar;
+}