diff --git a/src/core/mac/mac.cpp b/src/core/mac/mac.cpp
index b30c44eb2..8621a3a85 100644
--- a/src/core/mac/mac.cpp
+++ b/src/core/mac/mac.cpp
@@ -1126,8 +1126,9 @@ void Mac::RadioSleep(void)
 
     if (mDelaySleep)
     {
-        // Restart delay sleep timer
+        // Start delay sleep timer
         mReceiveTimer.Start(kSleepDelay);
+        mDelaySleep = false;
     }
     else
 #endif