diff --git a/src/os/inc/osDef.h b/src/os/inc/osDef.h
index bbe0f98ec0..07fb5c283b 100644
--- a/src/os/inc/osDef.h
+++ b/src/os/inc/osDef.h
@@ -40,10 +40,9 @@ extern "C" {
 #define ASSERT(x)
 #endif
 
-#ifdef UNUSED
-#undefine UNUSED
-#endif
+#ifndef UNUSED
 #define UNUSED(x) ((void)(x))
+#endif
 
 #ifdef UNUSED_FUNC
 #undefine UNUSED_FUNC