diff --git a/include/mbedtls/md5.h b/include/mbedtls/md5.h
index 4f8c921..bbfcae1 100644
--- a/include/mbedtls/md5.h
+++ b/include/mbedtls/md5.h
@@ -36,6 +36,11 @@
 // Regular implementation
 //
 
+#if ( defined(__ARMCC_VERSION) || defined(_MSC_VER) ) && \
+    !defined(inline) && !defined(__cplusplus)
+#define inline __inline
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif