diff --git a/peglib.h b/peglib.h
index dc97278..087e31a 100644
--- a/peglib.h
+++ b/peglib.h
@@ -1323,7 +1323,7 @@ public:
             return static_cast<size_t>(-1);
         }
 
-        char32_t cp;
+        char32_t cp = 0;
         auto len = decode_codepoint(s, n, cp);
 
         if (!ranges_.empty()) {