diff --git a/t/t5510-fetch.sh b/t/t5510-fetch.sh
index 38321d19efb..454d896390c 100755
--- a/t/t5510-fetch.sh
+++ b/t/t5510-fetch.sh
@@ -682,6 +682,7 @@ test_expect_success 'fetching with auto-gc does not lock up' '
 	(
 		cd auto-gc &&
 		git config gc.autoPackLimit 1 &&
+		git config gc.autoDetach false &&
 		GIT_ASK_YESNO="$D/askyesno" git fetch >fetch.out 2>&1 &&
 		! grep "Should I try again" fetch.out
 	)