diff --git a/pycppad/adfun.cpp b/pycppad/adfun.cpp
index 10d03cb..f6f4026 100644
--- a/pycppad/adfun.cpp
+++ b/pycppad/adfun.cpp
@@ -482,6 +482,7 @@ namespace pycppad {
 			"# ifndef NDEBUG",
 			"Cannot use CompareChange when NDEBUG is defined"
 		);
+		return 0;
 	}
 # else
 	// CompareChange