diff --git a/include/polarssl/md5.h b/include/polarssl/md5.h
index df2a61b..bb0ebf3 100644
--- a/include/polarssl/md5.h
+++ b/include/polarssl/md5.h
@@ -27,7 +27,11 @@
 #ifndef POLARSSL_MD5_H
 #define POLARSSL_MD5_H
 
+#if !defined(POLARSSL_CONFIG_FILE)
 #include "config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 #include <string.h>