diff --git a/UnitTests/Text/HtmlAttributeTests.cs b/UnitTests/Text/HtmlAttributeTests.cs
index 2ae9208bef..0443f29e6e 100644
--- a/UnitTests/Text/HtmlAttributeTests.cs
+++ b/UnitTests/Text/HtmlAttributeTests.cs
@@ -61,6 +61,9 @@ public void TestToHtmlAttributeId ()
 
 				Assert.AreEqual (value, parsed, "Failed to parse the HtmlAttributeId value for {0}", value);
 			}
+
+			name = ((HtmlAttributeId) 1024).ToAttributeName ();
+			Assert.AreEqual ("1024", name, "ToAttributeName() for unknown value");
 		}
 	}
 }
diff --git a/UnitTests/Text/HtmlTagIdTests.cs b/UnitTests/Text/HtmlTagIdTests.cs
index eb57524768..87b1ef9efb 100644
--- a/UnitTests/Text/HtmlTagIdTests.cs
+++ b/UnitTests/Text/HtmlTagIdTests.cs
@@ -54,6 +54,9 @@ public void TestToHtmlTagId ()
 
 				Assert.AreEqual (value, parsed, "Failed to parse the HtmlTagId value for {0}", value);
 			}
+
+			name = ((HtmlTagId) 1024).ToHtmlTagName ();
+			Assert.AreEqual ("1024", name, "ToHtmlTagName() for unknown value");
 		}
 
 		[Test]
diff --git a/UnitTests/Text/HtmlTokenizerTests.cs b/UnitTests/Text/HtmlTokenizerTests.cs
index f32c158cac..ccdbaedc4b 100644
--- a/UnitTests/Text/HtmlTokenizerTests.cs
+++ b/UnitTests/Text/HtmlTokenizerTests.cs
@@ -41,6 +41,9 @@ public void TestArgumentExceptions ()
 			Assert.Throws<ArgumentNullException> (() => new HtmlTokenizer ((Stream) null, Encoding.UTF8));
 
 			Assert.Throws<ArgumentNullException> (() => new HtmlTokenizer (Stream.Null, null));
+
+			var nullTokenizer = new HtmlTokenizer (Stream.Null);
+			var utf8Tokenizer = new HtmlTokenizer (Stream.Null, Encoding.UTF8);
 		}
 
 		static string Quote (string text)