diff --git a/Tests/base/NSMethodSignature/general.m b/Tests/base/NSMethodSignature/general.m
index 226be9ede..eccffe6be 100644
--- a/Tests/base/NSMethodSignature/general.m
+++ b/Tests/base/NSMethodSignature/general.m
@@ -181,7 +181,7 @@ typedef struct _MySmallStruct MySmallStruct;
 
 -(const char *)runtimeSignatureForSelector:(SEL)selector
 {
-  GSMethod meth = GSGetMethod(isa, selector, YES, YES);
+  GSMethod meth = GSGetMethod(object_getClass(self), selector, YES, YES);
   return method_getTypeEncoding (meth);
 }