diff --git a/ports/zephyr/mphalport.c b/ports/zephyr/mphalport.c
index fa64c4afc96e..2c9503284327 100644
--- a/ports/zephyr/mphalport.c
+++ b/ports/zephyr/mphalport.c
@@ -54,15 +54,11 @@ void mp_hal_wait_sem(struct k_sem *sem, uint32_t timeout_ms) {
         mp_handle_pending(true);
         MP_THREAD_GIL_EXIT();
         k_timeout_t wait;
+        uint32_t dt = mp_hal_ticks_ms() - t0;
         if (timeout_ms == (uint32_t)-1) {
             wait = K_FOREVER;
         } else {
-            uint32_t dt = mp_hal_ticks_ms() - t0;
-            if (dt >= timeout_ms) {
-                MP_THREAD_GIL_ENTER();
-                return;
-            }
-            wait = K_MSEC(timeout_ms - dt);
+            wait = K_MSEC((timeout_ms > dt) ? (timeout_ms - dt) : 0);
         }
         k_poll(wait_events, sem ? 2 : 1, wait);
         if (wait_events[0].state == K_POLL_STATE_SIGNALED) {
@@ -73,5 +69,9 @@ void mp_hal_wait_sem(struct k_sem *sem, uint32_t timeout_ms) {
             MP_THREAD_GIL_ENTER();
             return;
         }
+        if (dt >= timeout_ms) {
+            MP_THREAD_GIL_ENTER();
+            return;
+        }
     }
 }