diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index b1559f8dd13..f8c4caa9630 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -4016,7 +4016,7 @@ module ts {
                     result &= related;
                 }
             }
-            else if (source.typeParameters || source.typeParameters) {
+            else if (source.typeParameters || target.typeParameters) {
                 return Ternary.False;
             }
             // Spec 1.0 Section 3.8.3 & 3.8.4:
@@ -5274,7 +5274,7 @@ module ts {
                         signatureList = [signature];
                     }
                     else if (!compareSignatures(signatureList[0], signature, /*compareReturnTypes*/ false, compareTypes)) {
-                        // Signatures arent identical, do not use
+                        // Signatures aren't identical, do not use
                         return undefined;
                     }
                     else {
diff --git a/tests/baselines/reference/genericAndNonGenericInheritedSignature1.errors.txt b/tests/baselines/reference/genericAndNonGenericInheritedSignature1.errors.txt
new file mode 100644
index 00000000000..63ff9d9313e
--- /dev/null
+++ b/tests/baselines/reference/genericAndNonGenericInheritedSignature1.errors.txt
@@ -0,0 +1,17 @@
+tests/cases/compiler/genericAndNonGenericInheritedSignature1.ts(7,11): error TS2320: Interface 'Hello' cannot simultaneously extend types 'Foo' and 'Bar'.
+  Named properties 'f' of types 'Foo' and 'Bar' are not identical.
+
+
+==== tests/cases/compiler/genericAndNonGenericInheritedSignature1.ts (1 errors) ====
+    interface Foo {
+        f(x: any): any;
+    }
+    interface Bar {
+        f<T>(x: T): T;
+    }
+    interface Hello extends Foo, Bar {
+              ~~~~~
+!!! error TS2320: Interface 'Hello' cannot simultaneously extend types 'Foo' and 'Bar'.
+!!! error TS2320:   Named properties 'f' of types 'Foo' and 'Bar' are not identical.
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/genericAndNonGenericInheritedSignature1.js b/tests/baselines/reference/genericAndNonGenericInheritedSignature1.js
new file mode 100644
index 00000000000..15ea71b1223
--- /dev/null
+++ b/tests/baselines/reference/genericAndNonGenericInheritedSignature1.js
@@ -0,0 +1,12 @@
+//// [genericAndNonGenericInheritedSignature1.ts]
+interface Foo {
+    f(x: any): any;
+}
+interface Bar {
+    f<T>(x: T): T;
+}
+interface Hello extends Foo, Bar {
+}
+
+
+//// [genericAndNonGenericInheritedSignature1.js]
diff --git a/tests/baselines/reference/genericAndNonGenericInheritedSignature2.errors.txt b/tests/baselines/reference/genericAndNonGenericInheritedSignature2.errors.txt
new file mode 100644
index 00000000000..05fdd68319e
--- /dev/null
+++ b/tests/baselines/reference/genericAndNonGenericInheritedSignature2.errors.txt
@@ -0,0 +1,17 @@
+tests/cases/compiler/genericAndNonGenericInheritedSignature2.ts(7,11): error TS2320: Interface 'Hello' cannot simultaneously extend types 'Bar' and 'Foo'.
+  Named properties 'f' of types 'Bar' and 'Foo' are not identical.
+
+
+==== tests/cases/compiler/genericAndNonGenericInheritedSignature2.ts (1 errors) ====
+    interface Foo {
+        f(x: any): any;
+    }
+    interface Bar {
+        f<T>(x: T): T;
+    }
+    interface Hello extends Bar, Foo {
+              ~~~~~
+!!! error TS2320: Interface 'Hello' cannot simultaneously extend types 'Bar' and 'Foo'.
+!!! error TS2320:   Named properties 'f' of types 'Bar' and 'Foo' are not identical.
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/genericAndNonGenericInheritedSignature2.js b/tests/baselines/reference/genericAndNonGenericInheritedSignature2.js
new file mode 100644
index 00000000000..d8353b81e98
--- /dev/null
+++ b/tests/baselines/reference/genericAndNonGenericInheritedSignature2.js
@@ -0,0 +1,12 @@
+//// [genericAndNonGenericInheritedSignature2.ts]
+interface Foo {
+    f(x: any): any;
+}
+interface Bar {
+    f<T>(x: T): T;
+}
+interface Hello extends Bar, Foo {
+}
+
+
+//// [genericAndNonGenericInheritedSignature2.js]
diff --git a/tests/cases/compiler/genericAndNonGenericInheritedSignature1.ts b/tests/cases/compiler/genericAndNonGenericInheritedSignature1.ts
new file mode 100644
index 00000000000..3e5aa480be4
--- /dev/null
+++ b/tests/cases/compiler/genericAndNonGenericInheritedSignature1.ts
@@ -0,0 +1,8 @@
+interface Foo {
+    f(x: any): any;
+}
+interface Bar {
+    f<T>(x: T): T;
+}
+interface Hello extends Foo, Bar {
+}
diff --git a/tests/cases/compiler/genericAndNonGenericInheritedSignature2.ts b/tests/cases/compiler/genericAndNonGenericInheritedSignature2.ts
new file mode 100644
index 00000000000..f35e2ffda98
--- /dev/null
+++ b/tests/cases/compiler/genericAndNonGenericInheritedSignature2.ts
@@ -0,0 +1,8 @@
+interface Foo {
+    f(x: any): any;
+}
+interface Bar {
+    f<T>(x: T): T;
+}
+interface Hello extends Bar, Foo {
+}