diff --git a/zsh-better-npm-completion.plugin.zsh b/zsh-better-npm-completion.plugin.zsh
index 68427eb..6fcb4ef 100644
--- a/zsh-better-npm-completion.plugin.zsh
+++ b/zsh-better-npm-completion.plugin.zsh
@@ -11,9 +11,9 @@ _zbnc_recursively_look_for() {
   local dir=$PWD
   while [ ! -e "$dir/$filename" ]; do
     dir=${dir%/*}
-    [ "$dir" = "" ] && break
+    [[ "$dir" = "" ]] && break
   done
-  [ ! "$dir" = "" ] && echo "$dir/$filename"
+  [[ ! "$dir" = "" ]] && echo "$dir/$filename"
 }
 
 _zbnc_parse_package_json_for_script_suggestions() {
@@ -29,7 +29,7 @@ _zbnc_parse_package_json_for_script_suggestions() {
 _zbnc_npm_install_completion() {
 
   # Only run on `npm install ?`
-  [ ! "$(_zbnc_no_of_npm_args)" = "3" ] && return
+  [[ ! "$(_zbnc_no_of_npm_args)" = "3" ]] && return
 
   # Reccomend cached modules
   _values $(ls ~/.npm)
@@ -41,20 +41,20 @@ _zbnc_npm_install_completion() {
 _zbnc_npm_run_completion() {
 
   # Only run on `npm run ?`
-  [ ! "$(_zbnc_no_of_npm_args)" = "3" ] && return
+  [[ ! "$(_zbnc_no_of_npm_args)" = "3" ]] && return
 
   # Look for a package.json file
   local package_json="$(_zbnc_recursively_look_for package.json)"
 
   # Return if we can't find package.json
-  [ "$package_json" = "" ] && return
+  [[ "$package_json" = "" ]] && return
 
   # Parse scripts in package.json
   local -a options
   options=(${(f)"$(_zbnc_parse_package_json_for_script_suggestions $package_json)"})
 
   # Return if we can't parse it
-  [ "$#options" = 0 ] && return
+  [[ "$#options" = 0 ]] && return
 
   # Load the completions
   _describe 'values' options
@@ -87,7 +87,7 @@ _zbnc_zsh_better_npm_completion() {
   esac
 
   # Fall back to default completion if we haven't done a custom one
-  [ $custom_completion = false ] && _zbnc_default_npm_completion
+  [[ $custom_completion = false ]] && _zbnc_default_npm_completion
 }
 
 compdef _zbnc_zsh_better_npm_completion npm