diff --git a/src/twn_util.c b/src/twn_util.c
index 29f9503..6be2b51 100644
--- a/src/twn_util.c
+++ b/src/twn_util.c
@@ -290,7 +290,7 @@ char *expand_asterisk(const char *mask, const char *to) {
     char *str = SDL_malloc(mask_len + to_len); /* NULL included, replacing the original asterisk */
     SDL_memcpy(str, mask, offset - mask);
     SDL_memcpy(str + (offset - mask), to, to_len);
+    /* NULL byte is copied from here */
     SDL_memcpy(str + (offset - mask) + to_len, offset + 1, mask_len - (offset - mask));
-    str[mask_len + to_len] = '\0';
     return str;
 }