diff --git a/rtos/TARGET_CORTEX/mbed_rtx_idle.cpp b/rtos/TARGET_CORTEX/mbed_rtx_idle.cpp
index 121229460e..1ea59c5b79 100644
--- a/rtos/TARGET_CORTEX/mbed_rtx_idle.cpp
+++ b/rtos/TARGET_CORTEX/mbed_rtx_idle.cpp
@@ -195,6 +195,14 @@ static void default_idle_hook(void)
     core_util_critical_section_exit();
 }
 
+#elif defined(FEATURE_UVISOR)
+
+static void default_idle_hook(void)
+{
+    /* uVisor can't sleep. See <https://github.com/ARMmbed/uvisor/issues/420>
+     * for details. */
+}
+
 #else
 
 static void default_idle_hook(void)