diff --git a/t/t5509-fetch-push-namespaces.sh b/t/t5509-fetch-push-namespaces.sh
index a67f792..f234dba 100755
--- a/t/t5509-fetch-push-namespaces.sh
+++ b/t/t5509-fetch-push-namespaces.sh
@@ -1,6 +1,9 @@
 #!/bin/sh
 
 test_description='fetch/push involving ref namespaces'
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+
 . ./test-lib.sh
 
 test_expect_success setup '