diff --git a/t/t5333-pseudo-merge-bitmaps.sh b/t/t5333-pseudo-merge-bitmaps.sh
index 56674db562..a21a3114d3 100755
--- a/t/t5333-pseudo-merge-bitmaps.sh
+++ b/t/t5333-pseudo-merge-bitmaps.sh
@@ -234,8 +234,8 @@ test_expect_success 'pseudo-merge pattern with capture groups' '
 			test_commit_bulk 16 &&
 
 			git rev-list HEAD~16.. >in &&
-			sed "s|\(.*\)|create refs/remotes/$r/tags/\1 \1" in |
-			git update-ref --stdin || return 1
+			sed "s|\(.*\)|create refs/remotes/$r/tags/\1 \1|" in >refs &&
+			git update-ref --stdin <refs || return 1
 		done &&
 
 		git \