diff --git a/src/cmock.h b/src/cmock.h
index d566375..a313448 100644
--- a/src/cmock.h
+++ b/src/cmock.h
@@ -18,7 +18,7 @@
 
 #define CMOCK_ARG_MODE    CMOCK_MEM_INDEX_TYPE
 #define CMOCK_ARG_ALL     0
-#define CMOCK_ARG_NONE    ((CMOCK_MEM_INDEX_TYPE)(~0))
+#define CMOCK_ARG_NONE    ((CMOCK_MEM_INDEX_TYPE)(~0U))
 
 //-------------------------------------------------------
 // Memory API