diff --git a/wolfssl/internal.h b/wolfssl/internal.h
index b31e99c54..c42bd683d 100644
--- a/wolfssl/internal.h
+++ b/wolfssl/internal.h
@@ -152,11 +152,11 @@
 #elif defined(WOLFSSL_CMSIS_RTOSv2)
     #include "cmsis_os2.h"
 #elif defined(WOLFSSL_MDK_ARM)
-    #if !defined(WOLFSSL_MDK5)
-#include "cmsis_os.h"
-#else
-#include <rtl.h>
-#endif
+    #if defined(WOLFSSL_MDK5)
+        #include "cmsis_os.h"
+    #else
+        #include <rtl.h>
+    #endif
 #elif defined(MBED)
 #elif defined(WOLFSSL_TIRTOS)
     /* do nothing */