diff --git a/boot/zephyr/main.c b/boot/zephyr/main.c
index b375656..a4f87e9 100644
--- a/boot/zephyr/main.c
+++ b/boot/zephyr/main.c
@@ -390,7 +390,11 @@
 
     if (detect_value == expected) {
         if (delay > 0) {
+#ifdef CONFIG_MULTITHREADING
             k_sleep(K_MSEC(50));
+#else
+            k_busy_wait(50000);
+#endif
 
             /* Get the uptime for debounce purposes. */
             int64_t timestamp = k_uptime_get();
@@ -409,7 +413,11 @@
                 }
 
                 /* Delay 1 ms */
+#ifdef CONFIG_MULTITHREADING
                 k_sleep(K_MSEC(1));
+#else
+                k_busy_wait(1000);
+#endif
             }
         }
     }