diff --git a/lib/puppet/parser/functions/is_domain_name.rb b/lib/puppet/parser/functions/is_domain_name.rb
index 4e92939..5826dc0 100644
--- a/lib/puppet/parser/functions/is_domain_name.rb
+++ b/lib/puppet/parser/functions/is_domain_name.rb
@@ -4,7 +4,7 @@
 
 module Puppet::Parser::Functions
   newfunction(:is_domain_name, :type => :rvalue, :doc => <<-EOS
-Returns true if the string passed to this function is a valid IP address. Support for IPv4 and IPv6 address types is included.
+Returns true if the string passed to this function is a syntactically correct domain name.
     EOS
   ) do |arguments|
 
@@ -15,11 +15,31 @@ Returns true if the string passed to this function is a valid IP address. Suppor
 
     domain = arguments[0]
 
-    if domain =~ /^(([a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])\.?$/ then
-      return true
-    else
-      return false
+    # Limits (rfc1035, 3.1)
+    domain_max_length=255
+    label_min_length=1
+    label_max_length=63
+
+    # Allow ".", it is the top level domain
+    return true if domain == '.'
+
+    # Remove the final dot, if present.
+    domain.chomp!('.')
+
+    # Check the whole domain
+    return false if domain.empty?
+    return false if domain.length > domain_max_length
+
+    # Check each label in the domain
+    labels = domain.split('.')
+    vlabels = labels.each do |label|
+      break if label.length < label_min_length
+      break if label.length > label_max_length
+      break if label[-1..-1] == '-'
+      break if label[0..0] == '-'
+      break unless /^[a-z\d-]+$/i.match(label)
     end
+    return vlabels == labels
 
   end
 end
diff --git a/spec/unit/puppet/parser/functions/is_domain_name_spec.rb b/spec/unit/puppet/parser/functions/is_domain_name_spec.rb
index ec7c7f5..ccd3276 100644
--- a/spec/unit/puppet/parser/functions/is_domain_name_spec.rb
+++ b/spec/unit/puppet/parser/functions/is_domain_name_spec.rb
@@ -6,51 +6,63 @@ describe "the is_domain_name function" 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("is_domain_name").should == "function_is_domain_name"
   end
 
   it "should raise a ParseError if there is less than 1 arguments" do
-    lambda { @scope.function_is_domain_name([]) }.should( raise_error(Puppet::ParseError))
+    lambda { scope.function_is_domain_name([]) }.should( raise_error(Puppet::ParseError))
+  end
+
+  it "should return true if a valid short domain name" do
+    result = scope.function_is_domain_name(["x.com"])
+    result.should(be_true)
+  end
+
+  it "should return true if the domain is ." do
+    result = scope.function_is_domain_name(["."])
+    result.should(be_true)
+  end
+
+  it "should return true if the domain is x.com." do
+    result = scope.function_is_domain_name(["x.com."])
+    result.should(be_true)
   end
 
   it "should return true if a valid domain name" do
-    result = @scope.function_is_domain_name(["foo.bar.com"])
+    result = scope.function_is_domain_name(["foo.bar.com"])
     result.should(be_true)
   end
 
   it "should allow domain parts to start with numbers" do
-    result = @scope.function_is_domain_name(["3foo.2bar.com"])
+    result = scope.function_is_domain_name(["3foo.2bar.com"])
     result.should(be_true)
   end
 
   it "should allow domain to end with a dot" do
-    result = @scope.function_is_domain_name(["3foo.2bar.com."])
+    result = scope.function_is_domain_name(["3foo.2bar.com."])
     result.should(be_true)
   end
 
   it "should allow a single part domain" do
-    result = @scope.function_is_domain_name(["orange"])
+    result = scope.function_is_domain_name(["orange"])
     result.should(be_true)
   end
 
   it "should return false if domain parts start with hyphens" do
-    result = @scope.function_is_domain_name(["-3foo.2bar.com"])
+    result = scope.function_is_domain_name(["-3foo.2bar.com"])
     result.should(be_false)
   end
 
   it "should return true if domain contains hyphens" do
-    result = @scope.function_is_domain_name(["3foo-bar.2bar-fuzz.com"])
+    result = scope.function_is_domain_name(["3foo-bar.2bar-fuzz.com"])
     result.should(be_true)
   end
 
   it "should return false if domain name contains spaces" do
-    result = @scope.function_is_domain_name(["not valid"])
+    result = scope.function_is_domain_name(["not valid"])
     result.should(be_false)
   end
-
 end