diff --git a/extmod/re1.5/compilecode.c b/extmod/re1.5/compilecode.c
index 7a1b98128b..e4635f034a 100644
--- a/extmod/re1.5/compilecode.c
+++ b/extmod/re1.5/compilecode.c
@@ -65,7 +65,7 @@ static const char *_compilecode(const char *re, ByteProg *prog, int sizecode)
         }
         case '(': {
             term = PC;
-            int sub;
+            int sub = 0;
             int capture = re[1] != '?' || re[2] != ':';
 
             if (capture) {