diff --git a/source/lib/replace/snprintf.c b/source/lib/replace/snprintf.c
index 9f8a765..a174dcf 100644
--- a/source/lib/replace/snprintf.c
+++ b/source/lib/replace/snprintf.c
@@ -1264,7 +1264,7 @@ static int add_cnk_list_entry(struct pr_chunk_x **list,
 	VA_COPY(ap2, ap);
 	ret = vsnprintf(NULL, 0, format, ap2);
 	va_end(ap2);
-	if (ret <= 0) return ret;
+	if (ret < 0) return ret;
 
 	(*ptr) = (char *)malloc(ret+1);
 	if (!*ptr) return -1;