diff --git a/packages/oslo-concurrency.nix b/packages/oslo-concurrency.nix
index 7675ae2..42f7490 100644
--- a/packages/oslo-concurrency.nix
+++ b/packages/oslo-concurrency.nix
@@ -52,7 +52,7 @@ python3Packages.buildPythonPackage rec {
   ];
 
   checkPhase = ''
-    stestr run --exclude-regex ".*lock_with.*"
+    stestr run --exclude-regex ".*lock_with.*|test_core_size"
   '';
 
   src = fetchPypi {