diff --git a/py/frozenmod.c b/py/frozenmod.c
index 84df30b895..440ae0aacf 100644
--- a/py/frozenmod.c
+++ b/py/frozenmod.c
@@ -46,7 +46,7 @@ mp_lexer_t *mp_find_frozen_module(const char *str, int len) {
             mp_lexer_t *lex = mp_lexer_new_from_str_len(MP_QSTR_, s, *sz_ptr, 0);
             return lex;
         }
-        s += l + 1 + *sz_ptr++;
+        s += (l + 1) + (*sz_ptr++ + 1);
     }
     return NULL;
 }
diff --git a/tools/make-frozen.py b/tools/make-frozen.py
index 18368e218f..7c3865cc41 100755
--- a/tools/make-frozen.py
+++ b/tools/make-frozen.py
@@ -55,5 +55,5 @@ for f, st in modules:
         data = data[1:]
     data = data[1:-1]
     data = data.replace('"', '\\"')
-    print('"%s"' % data)
+    print('"%s\\0"' % data)
 print("};")