diff --git a/include/polarssl/sha256.h b/include/polarssl/sha256.h
index 89df578..f3c00fa 100644
--- a/include/polarssl/sha256.h
+++ b/include/polarssl/sha256.h
@@ -27,7 +27,11 @@
 #ifndef POLARSSL_SHA256_H
 #define POLARSSL_SHA256_H
 
+#if !defined(POLARSSL_CONFIG_FILE)
 #include "config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 #include <string.h>