From ee8d816738c19928c82a01a35ac2c1c307be7a8a Mon Sep 17 00:00:00 2001
From: Calvin Rose <calsrose@gmail.com>
Date: Fri, 23 Jan 2026 08:30:15 -0600
Subject: [PATCH] Fix test case.

---
 src/core/os.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/core/os.c b/src/core/os.c
index c075d29a..62a15b2c 100644
--- a/src/core/os.c
+++ b/src/core/os.c
@@ -1937,7 +1937,10 @@ JANET_CORE_FN(os_strftime,
     const char *p = fmt;
     while (*p) {
         if (*p++ == '%') {
-            if (!*p || !strchr(valid, *p)) {
+            if (!*p) {
+                janet_panic("invalid conversion specifier");
+            }
+            if (!strchr(valid, *p)) {
                 janet_panicf("invalid conversion specifier '%%%c'", *p);
             }
             p++;