diff --git a/.github/workflows/cultmesh-portability.yml b/.github/workflows/cultmesh-portability.yml
index c211d494..1a838e94 100644
--- a/.github/workflows/cultmesh-portability.yml
+++ b/.github/workflows/cultmesh-portability.yml
@@ -129,8 +129,11 @@ jobs:
 
       # tests/GameCult.Caching.Tests, the C# reference cache's own suite (about 1,260 tests, under a minute), ran in no
       # forge workflow; only the Mesh tests above exercised the reference.
+      # The forge runner is globalization-invariant, so ADeterministicIdIsTheSameUnderEveryCulture... cannot construct a
+      # culture and throws CultureNotFoundException; it is excluded here and still runs wherever ICU is present
+      # (variants:follow_up:culture-test-invariant-image).
       - name: Verify the CultCache document owner with the C# reference
-        run: dotnet test tests/GameCult.Caching.Tests/GameCult.Caching.Tests.csproj --logger "console;verbosity=minimal"
+        run: dotnet test tests/GameCult.Caching.Tests/GameCult.Caching.Tests.csproj --filter "FullyQualifiedName!~ADeterministicIdIsTheSameUnderEveryCulture" --logger "console;verbosity=minimal"
 
       # Packs the four TypeScript packages and installs them into a clean consumer, so a package that builds but does
       # not install or load fails here.