diff --git a/test/test_helper.rb b/test/test_helper.rb
index <HASH>..<HASH> 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -41,7 +41,9 @@ module Minitest
     end
 
     def teardown
-      refute FakeFS.activated?
+      return if !FakeFS.activated?
+      FakeFs.deactivate!
+      flunk "always deactivate FakeFs after test run"
     end
   end
 end
make activation bugs obvious but also fix them so only 1 test fails