diff --git a/sys/vfs/vfs.c b/sys/vfs/vfs.c
index a97ea1f678..9b16753310 100644
--- a/sys/vfs/vfs.c
+++ b/sys/vfs/vfs.c
@@ -736,7 +736,7 @@ int vfs_normalize_path(char *buf, const char *path, size_t buflen)
     }
 
     while(path <= path_end) {
-        DEBUG("vfs_normalize_path: + %d \"%.*s\" <- \"%s\" (%p)\n", npathcomp, len, buf, path, path);
+        DEBUG("vfs_normalize_path: + %d \"%.*s\" <- \"%s\" (%p)\n", npathcomp, (int)len, buf, path, path);
         if (path[0] == '\0') {
             break;
         }