diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index 10349d5..7edfe4b 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -639,6 +639,13 @@
 {
 	struct k_itimer *timr;
 
+	/*
+	 * timer_t could be any type >= int and we want to make sure any
+	 * @timer_id outside positive int range fails lookup.
+	 */
+	if ((unsigned long long)timer_id > INT_MAX)
+		return NULL;
+
 	rcu_read_lock();
 	timr = idr_find(&posix_timers_id, (int)timer_id);
 	if (timr) {