diff --git a/Source/OCMock/OCPartialMockObject.m b/Source/OCMock/OCPartialMockObject.m
index 6a7c53c3..1d7891f1 100644
--- a/Source/OCMock/OCPartialMockObject.m
+++ b/Source/OCMock/OCPartialMockObject.m
@@ -214,7 +214,8 @@ - (void)setupForwarderForSelector:(SEL)sel
     Class subclass = object_getClass([self realObject]);
     IMP forwarderIMP = [mockedClass instanceMethodForwarderForSelector:sel];
     class_replaceMethod(subclass, sel, forwarderIMP, types);
-    class_addMethod(subclass, aliasSelector, originalIMP, types);
+    if(originalIMP != NULL)
+        class_addMethod(subclass, aliasSelector, originalIMP, types);
 }