diff --git a/tools/install.sh b/tools/install.sh
index 314affe6c..ff99d34bd 100755
--- a/tools/install.sh
+++ b/tools/install.sh
@@ -1,3 +1,5 @@
+#!/bin/sh
+
 ZSH=`/usr/bin/env|grep 'ZSH='|cut -d '=' -f 2`
 if [ -d "$ZSH" ]
 then
diff --git a/tools/require_tool.sh b/tools/require_tool.sh
index 1fa77f77a..6e66f6fc5 100755
--- a/tools/require_tool.sh
+++ b/tools/require_tool.sh
@@ -1,3 +1,5 @@
+#!/bin/sh
+
 __require_tool_version_compare ()
 {
   (
diff --git a/tools/uninstall.sh b/tools/uninstall.sh
index 41d601576..913f86563 100644
--- a/tools/uninstall.sh
+++ b/tools/uninstall.sh
@@ -1,3 +1,5 @@
+#!/bin/sh
+
 echo "Removing ~/.oh-my-zsh"
 if [[ -d ~/.oh-my-zsh ]]
 then
diff --git a/tools/upgrade.sh b/tools/upgrade.sh
index 9a8497d96..bf3d66cb8 100644
--- a/tools/upgrade.sh
+++ b/tools/upgrade.sh
@@ -1,3 +1,5 @@
+#!/bin/sh
+
 printf '\033[0;34m%s\033[0m\n' "Upgrading Oh My Zsh"
 cd "$ZSH"
 if git pull --rebase --stat origin master