diff --git a/meta/git/hooks/pre-push b/meta/git/hooks/pre-push
index 868a977..3b4d74b 100755
--- a/meta/git/hooks/pre-push
+++ b/meta/git/hooks/pre-push
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 # A hook script to verify what is about to be pushed.  Called by "git push"
 # after it has checked the remote status, but before anything has been pushed.
@@ -27,9 +27,10 @@ url="$2"
 zero=$(git hash-object --stdin </dev/null | tr '[0-9a-f]' '0')
 
 # look for WIP at beginning or end of branch name
+is_wip_branch=1
 git rev-parse --symbolic-full-name --abbrev-ref HEAD \
-	| grep -Eqi '^wip($|[^[:alpha:]])|(^|[^[:alpha:]])wip$'
-is_wip_branch=$((! $?))
+	| grep -Eqi '^wip($|[^[:alpha:]])|(^|[^[:alpha:]])wip$' \
+	|| is_wip_branch=0
 
 while read local_ref local_oid remote_ref remote_oid; do
 	[ "$local_oid" != "$zero" ] || continue
@@ -46,7 +47,7 @@ while read local_ref local_oid remote_ref remote_oid; do
 	pattern='^(WIP|(fixup|squash)!)'
 
 	commits="$(git rev-list -E --oneline --grep "$pattern" "$range")"
-	if [ -n "$commits" ] && ((!is_wip_branch)); then
+	if [ -n "$commits" ] && [ "$is_wip_branch" -eq 0 ]; then
 		printf >&2 "%s: Commits in progress:\n" "$local_ref"
 		printf >&2 "%s\n" "$commits"
 		printf >&2 "Aborting push\n"