diff --git a/lib/sass/script/functions.rb b/lib/sass/script/functions.rb
index e647815c..35fa71eb 100644
--- a/lib/sass/script/functions.rb
+++ b/lib/sass/script/functions.rb
@@ -27,8 +27,13 @@ module Sass::Script
     # hue is in degrees,
     # and saturation and lightness are percentages.
     def hsl(h, s, l)
+      original_s = s
+      original_l = l
       # This algorithm is from http://www.w3.org/TR/css3-color#hsl-color
       h, s, l = [h, s, l].map { |a| a.value }
+      raise ArgumentError.new("Saturation #{s} must be between 0% and 100%") if s < 0 || s > 100
+      raise ArgumentError.new("Lightness #{l} must be between 0% and 100%") if l < 0 || l > 100
+
       h = (h % 360) / 360.0
       s /= 100.0
       l /= 100.0
diff --git a/test/sass/functions_test.rb b/test/sass/functions_test.rb
index 3b93f0c5..8be04739 100644
--- a/test/sass/functions_test.rb
+++ b/test/sass/functions_test.rb
@@ -43,6 +43,11 @@ class SassFunctionTest < Test::Unit::TestCase
     assert_rgb_hsl(purple, ['2820', '100%', '50%'])
   end
 
+  def test_hsl_checks_bounds
+    assert_error_message("Saturation -114 must be between 0% and 100% for `hsl'", "hsl(10, -114, 12)");
+    assert_error_message("Lightness 256 must be between 0% and 100% for `hsl'", "hsl(10, 10, 256%)");
+  end
+
   def test_percentage
     assert_equal("50%",  evaluate("percentage(.5)"))
     assert_equal("100%", evaluate("percentage(1)"))
@@ -81,12 +86,10 @@ class SassFunctionTest < Test::Unit::TestCase
   end
 
   def assert_error_message(message, value)
-    begin
-      evaluate(value)
-      flunk("Error message expected but not raised: #{message}")
-    rescue Sass::SyntaxError => e
-      assert_equal(message, e.message)
-    end
+    evaluate(value)
+    flunk("Error message expected but not raised: #{message}")
+  rescue Sass::SyntaxError => e
+    assert_equal(message, e.message)
   end
 
 end