diff --git a/src/insexpand.c b/src/insexpand.c
index 0ecb656..9c598a8 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -786,7 +786,8 @@
 	{
 	    if (!match_at_original_text(match)
 		    && STRNCMP(match->cp_str, str, len) == 0
-		    && match->cp_str[len] == NUL)
+		    && ((int)STRLEN(match->cp_str) <= len
+						 || match->cp_str[len] == NUL))
 		return NOTDONE;
 	    match = match->cp_next;
 	} while (match != NULL && !is_first_match(match));