This script depends on Bash-only features, and so should not be executed with sh.
diff --git a/README.mdown b/README.mdown
index 16ac662..9b2b969 100644
--- a/README.mdown
+++ b/README.mdown
@@ -34,7 +34,7 @@
 Another easy way to install git-flow is using Rick Osborne's excellent git-flow
 installer, which can be run using the following command:
 
-	$ wget --no-check-certificate -q -O - https://github.com/nvie/gitflow/raw/develop/contrib/gitflow-installer.sh | sudo sh
+	$ wget --no-check-certificate -q -O - https://github.com/nvie/gitflow/raw/develop/contrib/gitflow-installer.sh | sudo bash
 
 ### Windows
 
@@ -46,7 +46,7 @@
 first to install tools like `git`, `util-linux` and `wget` (with those three being packages that can be selected
 during installation). Then simply run this command from a Cygwin shell:
 
-	$ wget -q -O - https://github.com/nvie/gitflow/raw/develop/contrib/gitflow-installer.sh | sh
+	$ wget -q -O - https://github.com/nvie/gitflow/raw/develop/contrib/gitflow-installer.sh | bash
 
 #### Using [msysgit](http://code.google.com/p/msysgit/)
 Download and install `getopt.exe` from the [util-linux package](http://gnuwin32.sourceforge.net/packages/util-linux-ng.htm) into `C:\Program Files\Git\bin`. (Only `getopt.exe`, the others util-linux files are not used).
diff --git a/contrib/gitflow-installer.sh b/contrib/gitflow-installer.sh
index 33dbe58..bb803f4 100644
--- a/contrib/gitflow-installer.sh
+++ b/contrib/gitflow-installer.sh
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # git-flow make-less installer for *nix systems, by Rick Osborne
 # Based on the git-flow core Makefile: