diff --git a/install.sh b/install.sh
index 08b7ed9..bab8e3e 100755
--- a/install.sh
+++ b/install.sh
@@ -18,7 +18,7 @@ sudo xcode-select --install || true
 
 # Install homebrew
 export HOMEBREW_NO_ENV_HINTS=true
-if test ! $(which brew)
+if ! command -v brew >/dev/null 2>&1
 then
   echo "$PREFIX Installing brew..."
   /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"
@@ -46,12 +46,12 @@ done
 
 # Install oh-my-zsh
 OMZ=~/.oh-my-zsh
-if test ! -d $OMZ
+if test ! -d "$OMZ"
 then
   echo "> Installing oh my zsh..."
   curl -L http://install.ohmyz.sh | sh
 fi
-mkdir -p $OMZ/completions
+mkdir -p "$OMZ/completions"
 
 
 echo "$PREFIX Install global python packages..."