diff --git a/emper/CountingPrivateSemaphore.cpp b/emper/CountingPrivateSemaphore.cpp
index a74246a3ad540b112118fb6e8feefbe6065880bf..d66634c77a22d90f5adee0113aeaaf53412c852c 100644
--- a/emper/CountingPrivateSemaphore.cpp
+++ b/emper/CountingPrivateSemaphore.cpp
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
-// Copyright © 2020 Florian Schmaus
+// Copyright © 2020-2021 Florian Schmaus
 #include "CountingPrivateSemaphore.hpp"
 
 #include <cassert>	// for assert
@@ -46,7 +46,7 @@ auto CountingPrivateSemaphore::signalInternal() -> Context* {
 		// returns nullptr. In this case the block() function will
 		// have won the race.
 		Context* context = blockedContext.exchange(nullptr);
-		assert(context > (Context*)4096);
+		assert(!context || context > (Context*)4096);
 		return context;
 	}