diff --git a/Objective-J/Runtime.js b/Objective-J/Runtime.js
index 9188017c2..3b816d4ca 100644
--- a/Objective-J/Runtime.js
+++ b/Objective-J/Runtime.js
@@ -1031,13 +1031,29 @@ GLOBAL(method_getTypes) = function(/*Method*/ aMethod)
 GLOBAL(method_copyReturnType) = function(/*Method*/ aMethod)
 {
     var types = aMethod.method_types;
-    return types ? types[0] : NULL;
+
+    if (types)
+    {
+        var argType = types[0];
+
+        return argType != NULL ? argType : NULL;
+    }
+    else
+        return NULL;
 }
 
 GLOBAL(method_copyArgumentType) = function(/*Method*/ aMethod, /*unsigned int*/ index)
 {
     var types = aMethod.method_types;
-    return types ? types[index + 1] : NULL;
+
+    if (types)
+    {
+        var argType = types[index + 1];
+
+        return argType != NULL ? argType : NULL;
+    }
+    else
+        return NULL;
 }
 
 GLOBAL(method_getImplementation) = function(/*Method*/ aMethod)