diff --git a/src/node_file.cc b/src/node_file.cc
index 128ac51e3..926dcd667 100644
--- a/src/node_file.cc
+++ b/src/node_file.cc
@@ -162,10 +162,13 @@ static void After(uv_fs_t *req) {
           for (int i = 0; i < nnames; i++) {
             Local<String> name = String::New(namebuf);
             names->Set(Integer::New(i), name);
+#ifndef NDEBUG
             namebuf += strlen(namebuf);
             assert(*namebuf == '\0');
             namebuf += 1;
+#else
             namebuf += strlen(namebuf) + 1;
+#endif
           }
 
           argv[1] = names;