diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/HighlightingColorizer.cs b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/HighlightingColorizer.cs
index 10527b3843..6867f87c24 100644
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/HighlightingColorizer.cs
+++ b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/HighlightingColorizer.cs
@@ -256,7 +256,7 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 				if (b != null)
 					element.BackgroundBrush = b;
 			}
-			if (color.FontStyle != null || color.FontWeight != null || color.Underline != null) {
+			if (color.FontStyle != null || color.FontWeight != null) {
 				Typeface tf = element.TextRunProperties.Typeface;
 				element.TextRunProperties.SetTypeface(new Typeface(
 					tf.FontFamily,
diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/Resources/ModeV2.xsd b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/Resources/ModeV2.xsd
index 047ef38a19..171a1eb88d 100644
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/Resources/ModeV2.xsd
+++ b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/Resources/ModeV2.xsd
@@ -24,6 +24,7 @@
 	<xsd:simpleType name="FontStyle">
 		<xsd:restriction base="xsd:string">
 			<xsd:enumeration value="italic"/>
+		   <xsd:enumeration value="underlined"/>
 			<xsd:enumeration value="normal"/>
 			<xsd:enumeration value="oblique"/>
 		</xsd:restriction>
@@ -35,6 +36,7 @@
 		<xsd:attribute name="background" type="xsd:string" use="optional" />
 		<xsd:attribute name="fontWeight" type="FontWeight" use="optional" />
 		<xsd:attribute name="fontStyle" type="FontStyle" use="optional" />
+	   <xsd:attribute name="underline" type="xsd:boolean" use="optional" />
 		<xsd:anyAttribute namespace="##other" processContents="lax" />
 	</xsd:attributeGroup>