diff --git a/lib/cask.rb b/lib/cask.rb
index cd416d571c..132de309cf 100644
--- a/lib/cask.rb
+++ b/lib/cask.rb
@@ -45,11 +45,11 @@ class Cask
       ohai "We'll set permissions properly so we won't need sudo in the future"
       current_user = ENV['USER']
       if caskroom.parent.writable?
-        system "mkdir #{caskroom}"
+        system "/bin/mkdir #{caskroom}"
       else
         # sudo in system is rude.
-        system "sudo mkdir -p #{caskroom}"
-        system "sudo chown -R #{current_user}:staff #{caskroom.parent}"
+        system "/usr/bin/sudo /bin/mkdir -p #{caskroom}"
+        system "/usr/bin/sudo /usr/sbin/chown -R #{current_user}:staff #{caskroom.parent}"
       end
     end
     appdir.mkpath unless appdir.exist?
diff --git a/lib/cask/cli/home.rb b/lib/cask/cli/home.rb
index 481c2006a5..bac0cab5b6 100644
--- a/lib/cask/cli/home.rb
+++ b/lib/cask/cli/home.rb
@@ -3,7 +3,7 @@ module Cask::CLI::Home
     raise CaskUnspecifiedError if cask_names.empty?
     cask_names.each do |cask_name|
       cask = Cask.load(cask_name)
-      system "open", cask.homepage
+      system "/usr/bin/open", cask.homepage
     end
   end
 
diff --git a/lib/cask/system_command.rb b/lib/cask/system_command.rb
index 475cc05031..d39592f6ed 100644
--- a/lib/cask/system_command.rb
+++ b/lib/cask/system_command.rb
@@ -26,7 +26,7 @@ class Cask::SystemCommand
 
   def self._process_options(command, options)
     if options[:sudo]
-      command = "sudo -E #{_quote(command)}"
+      command = "/usr/bin/sudo -E #{_quote(command)}"
     end
     if options[:args]
       command = "#{command} #{options[:args].map { |arg| _quote(arg) }.join(' ')}"
diff --git a/test/cask/artifact/pkg_test.rb b/test/cask/artifact/pkg_test.rb
index 8b32473999..8dad93fa5d 100644
--- a/test/cask/artifact/pkg_test.rb
+++ b/test/cask/artifact/pkg_test.rb
@@ -12,7 +12,7 @@ describe Cask::Artifact::Pkg do
     it 'runs the system installer on the specified pkgs' do
       pkg = Cask::Artifact::Pkg.new(@cask, Cask::FakeSystemCommand)
 
-      expected_command = "sudo -E '/usr/sbin/installer' '-pkg' '#{@cask.destination_path/'MyFancyPkg'/'Fancy.pkg'}' '-target' '/' 2>&1"
+      expected_command = "/usr/bin/sudo -E '/usr/sbin/installer' '-pkg' '#{@cask.destination_path/'MyFancyPkg'/'Fancy.pkg'}' '-target' '/' 2>&1"
       Cask::FakeSystemCommand.stubs_command(expected_command)
 
       shutup do
@@ -27,10 +27,10 @@ describe Cask::Artifact::Pkg do
     it 'runs the specified uninstaller for the cask' do
       pkg = Cask::Artifact::Pkg.new(@cask, Cask::FakeSystemCommand)
 
-      Cask::FakeSystemCommand.stubs_command(%Q(sudo -E '/usr/bin/osascript' '-e' 'tell application "System Events" to count processes whose bundle identifier is "my.fancy.package.app"' 2>&1), '1')
-      Cask::FakeSystemCommand.stubs_command(%Q(sudo -E '/usr/bin/osascript' '-e' 'tell application id "my.fancy.package.app" to quit' 2>&1))
+      Cask::FakeSystemCommand.stubs_command(%Q(/usr/bin/sudo -E '/usr/bin/osascript' '-e' 'tell application "System Events" to count processes whose bundle identifier is "my.fancy.package.app"' 2>&1), '1')
+      Cask::FakeSystemCommand.stubs_command(%Q(/usr/bin/sudo -E '/usr/bin/osascript' '-e' 'tell application id "my.fancy.package.app" to quit' 2>&1))
 
-      expected_command = "sudo -E '#{@cask.destination_path/'MyFancyPkg'/'FancyUninstaller.tool'}' '--please' 2>&1"
+      expected_command = "/usr/bin/sudo -E '#{@cask.destination_path/'MyFancyPkg'/'FancyUninstaller.tool'}' '--please' 2>&1"
       Cask::FakeSystemCommand.stubs_command(expected_command)
 
       shutup do
@@ -82,9 +82,9 @@ describe Cask::Artifact::Pkg do
 </plist>
         PLIST
       )
-      Cask::FakeSystemCommand.stubs_command(%Q(sudo -E '/usr/sbin/kextstat' '-l' '-b' 'my.fancy.package.kernelextension' 2>&1), 'loaded')
-      Cask::FakeSystemCommand.expects_command(%Q(sudo -E '/sbin/kextunload' '-b' 'my.fancy.package.kernelextension' 2>&1))
-      Cask::FakeSystemCommand.stubs_command(%Q(sudo -E '/usr/sbin/pkgutil' '--forget' 'my.fancy.package.main' 2>&1))
+      Cask::FakeSystemCommand.stubs_command(%Q(/usr/bin/sudo -E '/usr/sbin/kextstat' '-l' '-b' 'my.fancy.package.kernelextension' 2>&1), 'loaded')
+      Cask::FakeSystemCommand.expects_command(%Q(/usr/bin/sudo -E '/sbin/kextunload' '-b' 'my.fancy.package.kernelextension' 2>&1))
+      Cask::FakeSystemCommand.stubs_command(%Q(/usr/bin/sudo -E '/usr/sbin/pkgutil' '--forget' 'my.fancy.package.main' 2>&1))
 
       Cask::FakeSystemCommand.stubs_command(
         %Q(/usr/sbin/pkgutil '--only-files' '--files' 'my.fancy.package.agent' 2>&1),
@@ -123,13 +123,13 @@ describe Cask::Artifact::Pkg do
         /tmp/fancy/bin
         /tmp/fancy/var
       ].each do |dir|
-        Cask::FakeSystemCommand.stubs_command(%Q(sudo -E '/bin/chmod' '777' '#{dir}' 2>&1))
+        Cask::FakeSystemCommand.stubs_command(%Q(/usr/bin/sudo -E '/bin/chmod' '777' '#{dir}' 2>&1))
       end
 
-      Cask::FakeSystemCommand.stubs_command(%Q(sudo -E '/usr/sbin/pkgutil' '--forget' 'my.fancy.package.agent' 2>&1))
+      Cask::FakeSystemCommand.stubs_command(%Q(/usr/bin/sudo -E '/usr/sbin/pkgutil' '--forget' 'my.fancy.package.agent' 2>&1))
 
-      Cask::FakeSystemCommand.stubs_command(%Q(sudo -E '/bin/rm' '-f' '/tmp/fancy/bin/fancy.exe' '/tmp/fancy/var/fancy.data' 2>&1))
-      Cask::FakeSystemCommand.stubs_command(%Q(sudo -E '/bin/rm' '-f' '/tmp/fancy/agent/fancy-agent.exe' '/tmp/fancy/agent/fancy-agent.pid' '/tmp/fancy/agent/fancy-agent.log' 2>&1))
+      Cask::FakeSystemCommand.stubs_command(%Q(/usr/bin/sudo -E '/bin/rm' '-f' '/tmp/fancy/bin/fancy.exe' '/tmp/fancy/var/fancy.data' 2>&1))
+      Cask::FakeSystemCommand.stubs_command(%Q(/usr/bin/sudo -E '/bin/rm' '-f' '/tmp/fancy/agent/fancy-agent.exe' '/tmp/fancy/agent/fancy-agent.pid' '/tmp/fancy/agent/fancy-agent.log' 2>&1))
 
       # No assertions after call since all assertions are implicit from the interactions setup above.
       # TODO: verify rmdir commands (requires setting up actual file tree or faking out .exists?
diff --git a/test/cask/cli/home_test.rb b/test/cask/cli/home_test.rb
index ebb4f21e7a..bb03ddb644 100644
--- a/test/cask/cli/home_test.rb
+++ b/test/cask/cli/home_test.rb
@@ -26,15 +26,15 @@ describe Cask::CLI::Home do
   it 'opens the homepage for the specified cask' do
     Cask::CLI::Home.run('alfred')
     Cask::CLI::Home.system_commands.must_equal [
-      ['open', 'http://www.alfredapp.com/']
+      ['/usr/bin/open', 'http://www.alfredapp.com/']
     ]
   end
 
   it 'works for multiple casks' do
     Cask::CLI::Home.run('alfred', 'adium')
     Cask::CLI::Home.system_commands.must_equal [
-      ['open', 'http://www.alfredapp.com/'],
-      ['open', 'https://www.adium.im/']
+      ['/usr/bin/open', 'http://www.alfredapp.com/'],
+      ['/usr/bin/open', 'https://www.adium.im/']
     ]
   end
 
diff --git a/test/cask/pkg_test.rb b/test/cask/pkg_test.rb
index e483f9f533..6c201f50b7 100644
--- a/test/cask/pkg_test.rb
+++ b/test/cask/pkg_test.rb
@@ -30,7 +30,7 @@ describe Cask::Pkg do
       )
 
       Cask::FakeSystemCommand.expects_command(
-        %q(sudo -E '/usr/sbin/pkgutil' '--forget' 'my.fake.pkg' 2>&1)
+        %q(/usr/bin/sudo -E '/usr/sbin/pkgutil' '--forget' 'my.fake.pkg' 2>&1)
       )
 
       pkg.uninstall