diff --git a/lib/puppet/parser/functions/generate.rb b/lib/puppet/parser/functions/generate.rb
index 91f7b2240..226a5b7e1 100644
--- a/lib/puppet/parser/functions/generate.rb
+++ b/lib/puppet/parser/functions/generate.rb
@@ -1,31 +1,37 @@
 # Runs an external command and returns the results
 Puppet::Parser::Functions::newfunction(:generate, :type => :rvalue,
     :doc => "Calls an external command on the Puppet master and returns
     the results of the command.  Any arguments are passed to the external command as
     arguments.  If the generator does not exit with return code of 0,
     the generator is considered to have failed and a parse error is
     thrown.  Generators can only have file separators, alphanumerics, dashes,
     and periods in them.  This function will attempt to protect you from
     malicious generator calls (e.g., those with '..' in them), but it can
     never be entirely safe.  No subshell is used to execute
     generators, so all shell metacharacters are passed directly to
     the generator.") do |args|
 
-      raise Puppet::ParseError, "Generators must be fully qualified" unless args[0] =~ /^#{File::SEPARATOR}/
+      raise Puppet::ParseError, "Generators must be fully qualified" unless Puppet::Util.absolute_path?(args[0])
 
-      unless args[0] =~ /^[-#{File::SEPARATOR}\w.]+$/
+      if Puppet.features.microsoft_windows?
+        valid = args[0] =~ /^[a-z]:(?:[\/\\][\w.-]+)+$/i
+      else
+        valid = args[0] =~ /^[-\/\w.]+$/
+      end
+
+      unless valid
         raise Puppet::ParseError,
           "Generators can only contain alphanumerics, file separators, and dashes"
       end
 
       if args[0] =~ /\.\./
         raise Puppet::ParseError,
           "Can not use generators with '..' in them."
       end
 
       begin
         Dir.chdir(File.dirname(args[0])) { Puppet::Util.execute(args) }
       rescue Puppet::ExecutionFailure => detail
         raise Puppet::ParseError, "Failed to execute generator #{args[0]}: #{detail}"
       end
 end
diff --git a/spec/unit/parser/functions/generate_spec.rb b/spec/unit/parser/functions/generate_spec.rb
index 6c90ae531..e50805393 100755
--- a/spec/unit/parser/functions/generate_spec.rb
+++ b/spec/unit/parser/functions/generate_spec.rb
@@ -1,43 +1,85 @@
 #!/usr/bin/env rspec
 require 'spec_helper'
 
 describe "the generate function" do
   before :all do
     Puppet::Parser::Functions.autoloader.loadall
   end
 
-  before :each do
-    @scope = Puppet::Parser::Scope.new
-  end
+  let(:scope) { Puppet::Parser::Scope.new }
 
   it "should exist" do
     Puppet::Parser::Functions.function("generate").should == "function_generate"
   end
 
-  it "should accept a fully-qualified path as a command" do
-    command = File::SEPARATOR + "command"
-    Puppet::Util.expects(:execute).with([command]).returns("yay")
-    lambda { @scope.function_generate([command]) }.should_not raise_error(Puppet::ParseError)
+  it " accept a fully-qualified path as a command" do
+    command = File.expand_path('/command/foo')
+    Dir.expects(:chdir).with(File.dirname(command)).returns("yay")
+    scope.function_generate([command]).should == "yay"
   end
 
   it "should not accept a relative path as a command" do
-    command = "command"
-    lambda { @scope.function_generate([command]) }.should raise_error(Puppet::ParseError)
+    lambda { scope.function_generate(["command"]) }.should raise_error(Puppet::ParseError)
+  end
+
+  it "should not accept a command containing illegal characters" do
+    lambda { scope.function_generate([File.expand_path('/##/command')]) }.should raise_error(Puppet::ParseError)
   end
 
-  # Really not sure how to implement this test, just sure it needs
-  # to be implemented.
-  it "should not accept a command containing illegal characters"
+  it "should not accept a command containing spaces" do
+    lambda { scope.function_generate([File.expand_path('/com mand')]) }.should raise_error(Puppet::ParseError)
+  end
 
   it "should not accept a command containing '..'" do
-    command = File::SEPARATOR + "command#{File::SEPARATOR}..#{File::SEPARATOR}"
-    lambda { @scope.function_generate([command]) }.should raise_error(Puppet::ParseError)
+    command = File.expand_path("/command/../")
+    lambda { scope.function_generate([command]) }.should raise_error(Puppet::ParseError)
   end
 
   it "should execute the generate script with the correct working directory" do
-    command = File::SEPARATOR + "command"
-    Dir.expects(:chdir).with(File.dirname(command)).yields
-    Puppet::Util.expects(:execute).with([command]).returns("yay")
-    lambda { @scope.function_generate([command]) }.should_not raise_error(Puppet::ParseError)
+    command = File.expand_path("/command")
+    Dir.expects(:chdir).with(File.dirname(command)).returns("yay")
+    scope.function_generate([command]).should == 'yay'
+  end
+
+  describe "on Windows" do
+    before :each do
+      Puppet.features.stubs(:microsoft_windows?).returns(true)
+    end
+
+    it "should accept lower-case drive letters" do
+      command = 'd:/command/foo'
+      Dir.expects(:chdir).with(File.dirname(command)).returns("yay")
+      scope.function_generate([command]).should == 'yay'
+    end
+
+    it "should accept upper-case drive letters" do
+      command = 'D:/command/foo'
+      Dir.expects(:chdir).with(File.dirname(command)).returns("yay")
+      scope.function_generate([command]).should == 'yay'
+    end
+
+    it "should accept forward and backslashes in the path" do
+      command = 'D:\command/foo\bar'
+      Dir.expects(:chdir).with(File.dirname(command)).returns("yay")
+      scope.function_generate([command]).should == 'yay'
+    end
+
+    it "should reject colons when not part of the drive letter" do
+      lambda { scope.function_generate(['C:/com:mand']) }.should raise_error(Puppet::ParseError)
+    end
+
+    it "should reject root drives" do
+      lambda { scope.function_generate(['C:/']) }.should raise_error(Puppet::ParseError)
+    end
+  end
+
+  describe "on non-Windows" do
+    before :each do
+      Puppet.features.stubs(:microsoft_windows?).returns(false)
+    end
+
+    it "should reject backslashes" do
+      lambda { scope.function_generate(['/com\\mand']) }.should raise_error(Puppet::ParseError)
+    end
   end
 end