diff --git a/mac b/mac
index d6be09731..70dd13dc1 100644
--- a/mac
+++ b/mac
@@ -34,7 +34,7 @@ if [[ -f /etc/zshenv ]]; then
 fi
 ### end mac-components/zsh-fix
 
-if (( $+commands[brew] )); then
+if (( ! $+commands[brew] )); then
   fancy_echo "Installing Homebrew, a good OS X package manager ..."
     ruby <(curl -fsS https://raw.github.com/mxcl/homebrew/go/install)
     brew update
diff --git a/mac-components/homebrew b/mac-components/homebrew
index 357ba3b67..48022ebd1 100644
--- a/mac-components/homebrew
+++ b/mac-components/homebrew
@@ -1,4 +1,4 @@
-if (( $+commands[brew] )); then
+if (( ! $+commands[brew] )); then
   fancy_echo "Installing Homebrew, a good OS X package manager ..."
     ruby <(curl -fsS https://raw.github.com/mxcl/homebrew/go/install)
     brew update