diff --git a/components/layout/multicol.rs b/components/layout/multicol.rs
index c1773fc0c63f..24d90069aa62 100644
--- a/components/layout/multicol.rs
+++ b/components/layout/multicol.rs
@@ -99,9 +99,11 @@ impl Flow for MulticolFlow {
         {
             let column_style = self.block_flow.fragment.style.get_column();
 
-            // `None` is 'normal': "UA-specified length. A value of 1em is suggested."
-            let column_gap = column_style.column_gap.0.unwrap_or_else(||
-                self.block_flow.fragment.style.get_font().font_size);
+            let column_gap = match column_style.column_gap {
+                Either::First(len) => len,
+                Either::Second(_normal) => self.block_flow.fragment.style.get_font().font_size,
+            };
+
             let mut column_count;
             if let Either::First(column_width) = column_style.column_width {
                 column_count =
diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index c424ca705a78..92987c01722b 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -2387,9 +2387,11 @@ clip-path
     ${impl_simple_copy('column_count', 'mColumnCount')}
 
     pub fn set_column_gap(&mut self, v: longhands::column_gap::computed_value::T) {
-        match v.0 {
-            Some(len) => self.gecko.mColumnGap.set(len),
-            None => self.gecko.mColumnGap.set_value(CoordDataValue::Normal),
+        use values::Either;
+
+        match v {
+            Either::First(len) => self.gecko.mColumnGap.set(len),
+            Either::Second(_normal) => self.gecko.mColumnGap.set_value(CoordDataValue::Normal),
         }
     }
 
diff --git a/components/style/properties/longhand/column.mako.rs b/components/style/properties/longhand/column.mako.rs
index a9e0880664e4..119c4e0ca31d 100644
--- a/components/style/properties/longhand/column.mako.rs
+++ b/components/style/properties/longhand/column.mako.rs
@@ -96,86 +96,12 @@ ${helpers.predefined_type("column-width",
 </%helpers:longhand>
 
 // FIXME: This prop should be animatable.
-<%helpers:longhand name="column-gap" experimental="True" animatable="False">
-    use std::fmt;
-    use style_traits::ToCss;
-    use values::HasViewportPercentage;
-
-    impl HasViewportPercentage for SpecifiedValue {
-        fn has_viewport_percentage(&self) -> bool {
-            match *self {
-                SpecifiedValue::Specified(length) => length.has_viewport_percentage(),
-                _ => false
-            }
-        }
-    }
-
-    #[derive(Debug, Clone, Copy, PartialEq)]
-    #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-    pub enum SpecifiedValue {
-        Normal,
-        Specified(specified::Length),
-    }
-
-    impl ToCss for SpecifiedValue {
-        fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
-            match *self {
-                SpecifiedValue::Normal => dest.write_str("normal"),
-                SpecifiedValue::Specified(l) => l.to_css(dest),
-            }
-        }
-    }
-
-    pub mod computed_value {
-        use app_units::Au;
-        #[derive(Debug, Clone, PartialEq)]
-        #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-        pub struct T(pub Option<Au>);
-    }
-
-    impl ToCss for computed_value::T {
-        fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
-            match self.0 {
-                None => dest.write_str("normal"),
-                Some(l) => l.to_css(dest),
-            }
-        }
-    }
-
-    #[inline]
-    pub fn get_initial_value() -> computed_value::T {
-        computed_value::T(None)
-    }
-
-    impl ToComputedValue for SpecifiedValue {
-        type ComputedValue = computed_value::T;
-
-        #[inline]
-        fn to_computed_value(&self, context: &Context) -> computed_value::T {
-            match *self {
-                SpecifiedValue::Normal => computed_value::T(None),
-                SpecifiedValue::Specified(l) =>
-                    computed_value::T(Some(l.to_computed_value(context)))
-            }
-        }
-        #[inline]
-        fn from_computed_value(computed: &computed_value::T) -> Self {
-            match *computed {
-                computed_value::T(None) => SpecifiedValue::Normal,
-                computed_value::T(Some(l)) =>
-                    SpecifiedValue::Specified(ToComputedValue::from_computed_value(&l))
-            }
-        }
-    }
-
-    pub fn parse(_context: &ParserContext, input: &mut Parser) -> Result<SpecifiedValue, ()> {
-        if input.try(|input| input.expect_ident_matching("normal")).is_ok() {
-            Ok(SpecifiedValue::Normal)
-        } else {
-            specified::Length::parse_non_negative(input).map(SpecifiedValue::Specified)
-        }
-    }
-</%helpers:longhand>
+${helpers.predefined_type("column-gap",
+                          "length::LengthOrNormal",
+                          "Either::Second(Normal)",
+                          parse_method='parse_non_negative_length',
+                          experimental=True,
+                          animatable=False)}
 
 ${helpers.single_keyword("column-fill", "auto balance",
                          products="gecko", animatable=False)}