diff --git a/rake/lib/rbenv.rb b/rake/lib/rbenv.rb
index 1180108a..d643b1a6 100644
--- a/rake/lib/rbenv.rb
+++ b/rake/lib/rbenv.rb
@@ -8,27 +8,27 @@ module Rbenv
     def self.bootstrap
         unless self.is_installed?
             BREWS.each { |pkg| Homebrew.install pkg }
-            sh 'exec $SHELL -l'
+            sh_safe 'exec $SHELL -l'
         end
     end
 
     def self.destroy
         if self.is_installed?
             BREWS.each { |pkg| Homebrew.remove pkg }
-            # sh "rm -rf #{Homebrew.prefix 'rbenv'}"
+            # sh_safe "rm -rf #{Homebrew.prefix 'rbenv'}"
         end
     end
 
     def self.install(version, gems=[])
         unless self.is_version_installed?(version)
-            sh "rbenv install #{version}"
+            sh_safe "rbenv install #{version}"
         end
-        sh "RBENV_VERSION=#{version} gem install #{gems.join(' ')}"
+        sh_safe "RBENV_VERSION=#{version} gem install #{gems.join(' ')}"
     end
 
     def self.update(version)
-        sh "RBENV_VERSION=#{version} gem update"
-        sh "RBENV_VERSION=#{version} gem clean"
+        sh_safe "RBENV_VERSION=#{version} gem update"
+        sh_safe "RBENV_VERSION=#{version} gem clean"
     end
 
     def self.is_installed?
@@ -36,7 +36,7 @@ module Rbenv
     end
 
     def self.is_version_installed?(version)
-        system("rbenv versions | grep -w #{version}")
+        system("rbenv versions | grep -w #{version} &>/dev/null")
     end
 
     def self.installed_versions