diff --git a/Library/Homebrew/cmd/update-bash.sh b/Library/Homebrew/cmd/update-bash.sh
index 3b3eac482fb1d9ac3cbac80a0f5d80f3aaf6a386..27cbd32ed7f677c3cdd8af6358d1a9c298023899 100755
--- a/Library/Homebrew/cmd/update-bash.sh
+++ b/Library/Homebrew/cmd/update-bash.sh
@@ -54,8 +54,8 @@ repo_var() {
 
 upstream_branch() {
   local upstream_branch
-  upstream_branch="$(git symbolic-ref refs/remotes/origin/HEAD 2>/dev/null |
-                     sed -e 's|refs/remotes/origin/||' )"
+  upstream_branch="$(git symbolic-ref refs/remotes/origin/HEAD 2>/dev/null)"
+  upstream_branch="${upstream_branch#refs/remotes/origin/}"
   [[ -z "$upstream_branch" ]] && upstream_branch="master"
   echo "$upstream_branch"
 }