diff --git a/library/md.c b/library/md.c
index dcdf7c9..cb720bb 100644
--- a/library/md.c
+++ b/library/md.c
@@ -225,7 +225,14 @@
     if( md_info == NULL )
         return 3;
 
+#if defined(POLARSSL_FS_IO)
     return md_info->file_func( path, output );
+#else
+    ((void) path);
+    ((void) output);
+
+    return POLARSSL_ERR_MD_FEATURE_UNAVAILABLE;
+#endif
 }
 
 int md_hmac_starts( md_context_t *ctx, const unsigned char *key, size_t keylen )