diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
index 7f767b5c38fe2c..cb51aee4cbf609 100755
--- a/contrib/subtree/git-subtree.sh
+++ b/contrib/subtree/git-subtree.sh
@@ -976,10 +976,10 @@ cmd_merge () {
 
 	if test -n "$arg_addmerge_message"
 	then
-		git merge -Xsubtree="$arg_prefix" \
+		git merge --no-ff -Xsubtree="$arg_prefix" \
 			--message="$arg_addmerge_message" "$rev"
 	else
-		git merge -Xsubtree="$arg_prefix" $rev
+		git merge --no-ff -Xsubtree="$arg_prefix" $rev
 	fi
 }