diff --git a/src/cindent.c b/src/cindent.c
index c7caed6..3dc7b16 100644
--- a/src/cindent.c
+++ b/src/cindent.c
@@ -582,6 +582,8 @@
 	for (s += 4; *s; ++s)
 	{
 	    s = cin_skipcomment(s);
+	    if (*s == NUL)
+		break;
 	    if (*s == ':')
 	    {
 		if (s[1] == ':')	// skip over "::" for C++