diff --git a/tests/unit/test_mdns.cpp b/tests/unit/test_mdns.cpp
index 0d1e5c204..4b8be85c6 100644
--- a/tests/unit/test_mdns.cpp
+++ b/tests/unit/test_mdns.cpp
@@ -4703,7 +4703,7 @@ void TestMultiPacket(void)
 
     Log("Since message is marked as `truncated`, mDNS should wait at least 400 msec");
 
-    AdvanceTime(400);
+    AdvanceTime(399);
     VerifyOrQuit(sDnsMessages.IsEmpty());
 
     AdvanceTime(2000);