diff --git a/src/core/s-unicode.c b/src/core/s-unicode.c
index dc8baf497d..ba9e6eb06e 100644
--- a/src/core/s-unicode.c
+++ b/src/core/s-unicode.c
@@ -392,7 +392,7 @@ Boolean isLegalUTF8Sequence(const UTF8 *source, const UTF8 *sourceEnd) {
 	const REBYTE *end = str + len;
 	const REBYTE *acc = str - 1;
 #ifdef USE_NEW_UTF8_DECODE
-	REBCNT codepoint;
+	REBCNT codepoint = 0;
 	REBCNT state = UTF8_ACCEPT;
 
 	for (; str < end; ++str) {