diff --git a/mongoose.h b/mongoose.h
index e8a2e087..e92e2ce3 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -1088,7 +1088,8 @@ int gettimeofday(struct timeval *tp, void *tzp);
 #define CS_COMMON_PLATFORMS_SIMPLELINK_CS_SIMPLELINK_H_
 
 /* If simplelink.h is already included, all bets are off. */
-#if MG_NET_IF == MG_NET_IF_SIMPLELINK && !defined(__SIMPLELINK_H__)
+#if defined(MG_NET_IF) && MG_NET_IF == MG_NET_IF_SIMPLELINK && \
+    !defined(__SIMPLELINK_H__)
 
 #include <stdbool.h>