diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 13bf7bb7b..0ce84d22b 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -170,6 +170,10 @@ job_integration_browser_ff_1:
     - export REMOTE_URL=http://192.168.122.175:4445/wd/hub
     - export BROWSER=firefox
     - export RAILS_SERVE_STATIC_FILES=true
+    - unset MAILBOX_AUTO1
+    - unset MAILBOX_AUTO2
+    - unset MAILBOX_MANUAL1
+    - unset MAILBOX_MANUAL2
     - script/build/test_db_config.sh production ci_zammad_browser_ff_1
     - script/build/test_db_config.sh test ci_zammad_browser_ff_1_test
     - script/build/test_slice_tests.sh 1
diff --git a/script/build/test_slice_tests.sh b/script/build/test_slice_tests.sh
index c3a10a120..2ac73ad18 100755
--- a/script/build/test_slice_tests.sh
+++ b/script/build/test_slice_tests.sh
@@ -11,11 +11,6 @@ if [ "$LEVEL" == '1' ]; then
   rm test/browser/prefereces_test.rb
   rm test/browser/setting_test.rb
 
-  unset MAILBOX_AUTO1
-  unset MAILBOX_AUTO2
-  unset MAILBOX_MANUAL1
-  unset MAILBOX_MANUAL2
-
 elif [ "$LEVEL" == '2' ]; then
   echo "slicing level 2"
 
@@ -36,11 +31,6 @@ elif [ "$LEVEL" == '2' ]; then
   rm test/browser/taskbar_task_test.rb
   rm test/browser/switch_to_user_test.rb
 
-  unset MAILBOX_AUTO1
-  unset MAILBOX_AUTO2
-  unset MAILBOX_MANUAL1
-  unset MAILBOX_MANUAL2
-
 elif [ "$LEVEL" == '3' ]; then
   echo "slicing level 3"