diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index 21e0c8d75fc..41fac1bd57a 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -718,23 +718,6 @@ def set_gecko_property(ffi_name, expr):
     }
 </%def>
 
-<%def name="impl_style_sides(ident)">
-    <% gecko_ffi_name = "m" + to_camel_case(ident) %>
-
-    #[allow(non_snake_case)]
-    pub fn set_${ident}(&mut self, v: longhands::${ident}::computed_value::T) {
-        v.to_gecko_rect(&mut self.gecko.${gecko_ffi_name});
-    }
-
-    <%self:copy_sides_style_coord ident="${ident}"></%self:copy_sides_style_coord>
-
-    #[allow(non_snake_case)]
-    pub fn clone_${ident}(&self) -> longhands::${ident}::computed_value::T {
-        longhands::${ident}::computed_value::T::from_gecko_rect(&self.gecko.${gecko_ffi_name})
-            .expect("clone for ${ident} failed")
-    }
-</%def>
-
 <%def name="copy_sides_style_coord(ident)">
     <% gecko_ffi_name = "m" + to_camel_case(ident) %>
     #[allow(non_snake_case)]
@@ -989,7 +972,7 @@ fn static_assert() {
 
 <%self:impl_trait style_struct_name="Border"
                   skip_longhands="${skip_border_longhands} border-image-source
-                                  border-image-repeat border-image-width">
+                                  border-image-repeat">
     % for side in SIDES:
     pub fn set_border_${side.ident}_style(&mut self, v: BorderStyle) {
         self.gecko.mBorderStyle[${side.index}] = v;
@@ -1128,8 +1111,6 @@ fn static_assert() {
         % endfor
         longhands::border_image_repeat::computed_value::T(servo_h, servo_v)
     }
-
-    <% impl_style_sides("border_image_width") %>
 </%self:impl_trait>
 
 <% skip_scroll_margin_longhands = " ".join(["scroll-margin-%s" % x.ident for x in SIDES]) %>
diff --git a/components/style/properties/longhands/border.mako.rs b/components/style/properties/longhands/border.mako.rs
index 7ea8b8dd0eb..7909372be17 100644
--- a/components/style/properties/longhands/border.mako.rs
+++ b/components/style/properties/longhands/border.mako.rs
@@ -159,60 +159,3 @@ ${helpers.predefined_type(
     flags="APPLIES_TO_FIRST_LETTER",
     boxed=True,
 )}
-
-// FIXME(emilio): Why does this live here? ;_;
-#[cfg(feature = "gecko")]
-impl crate::values::computed::BorderImageWidth {
-    pub fn to_gecko_rect(&self, sides: &mut crate::gecko_bindings::structs::nsStyleSides) {
-        use crate::gecko_bindings::sugar::ns_style_coord::{CoordDataMut, CoordDataValue};
-        use crate::gecko::values::GeckoStyleCoordConvertible;
-        use crate::values::generics::border::BorderImageSideWidth;
-
-        % for i in range(0, 4):
-        match self.${i} {
-            BorderImageSideWidth::Auto => {
-                sides.data_at_mut(${i}).set_value(CoordDataValue::Auto)
-            },
-            BorderImageSideWidth::Length(l) => {
-                l.to_gecko_style_coord(&mut sides.data_at_mut(${i}))
-            },
-            BorderImageSideWidth::Number(n) => {
-                sides.data_at_mut(${i}).set_value(CoordDataValue::Factor(n.0))
-            },
-        }
-        % endfor
-    }
-
-    pub fn from_gecko_rect(
-        sides: &crate::gecko_bindings::structs::nsStyleSides,
-    ) -> Option<crate::values::computed::BorderImageWidth> {
-        use crate::gecko_bindings::structs::nsStyleUnit::{eStyleUnit_Factor, eStyleUnit_Auto};
-        use crate::gecko_bindings::sugar::ns_style_coord::CoordData;
-        use crate::gecko::values::GeckoStyleCoordConvertible;
-        use crate::values::computed::{LengthPercentage, Number};
-        use crate::values::generics::border::BorderImageSideWidth;
-        use crate::values::generics::NonNegative;
-
-        Some(
-            crate::values::computed::BorderImageWidth::new(
-                % for i in range(0, 4):
-                match sides.data_at(${i}).unit() {
-                    eStyleUnit_Auto => {
-                        BorderImageSideWidth::Auto
-                    },
-                    eStyleUnit_Factor => {
-                        BorderImageSideWidth::Number(
-                            NonNegative(Number::from_gecko_style_coord(&sides.data_at(${i}))
-                                .expect("sides[${i}] could not convert to Number")))
-                    },
-                    _ => {
-                        BorderImageSideWidth::Length(
-                            NonNegative(LengthPercentage::from_gecko_style_coord(&sides.data_at(${i}))
-                                .expect("sides[${i}] could not convert to LengthPercentage")))
-                    },
-                },
-                % endfor
-            )
-        )
-    }
-}
diff --git a/components/style/values/computed/border.rs b/components/style/values/computed/border.rs
index 62c8e3883f6..908fd1436ac 100644
--- a/components/style/values/computed/border.rs
+++ b/components/style/values/computed/border.rs
@@ -7,7 +7,7 @@
 use crate::values::computed::length::{NonNegativeLength, NonNegativeLengthPercentage};
 use crate::values::computed::{NonNegativeNumber, NonNegativeNumberOrPercentage};
 use crate::values::generics::border::BorderCornerRadius as GenericBorderCornerRadius;
-use crate::values::generics::border::BorderImageSideWidth as GenericBorderImageSideWidth;
+use crate::values::generics::border::GenericBorderImageSideWidth;
 use crate::values::generics::border::BorderImageSlice as GenericBorderImageSlice;
 use crate::values::generics::border::BorderRadius as GenericBorderRadius;
 use crate::values::generics::border::BorderSpacing as GenericBorderSpacing;
diff --git a/components/style/values/generics/border.rs b/components/style/values/generics/border.rs
index ec0ab1c4b07..f36062ce39b 100644
--- a/components/style/values/generics/border.rs
+++ b/components/style/values/generics/border.rs
@@ -23,15 +23,18 @@ use style_traits::{CssWriter, ToCss};
     ToResolvedValue,
     ToShmem,
 )]
-pub enum BorderImageSideWidth<LengthPercentage, Number> {
+#[repr(C, u8)]
+pub enum GenericBorderImageSideWidth<LP, N> {
     /// `<length-or-percentage>`
-    Length(LengthPercentage),
+    LengthPercentage(LP),
     /// `<number>`
-    Number(Number),
+    Number(N),
     /// `auto`
     Auto,
 }
 
+pub use self::GenericBorderImageSideWidth as BorderImageSideWidth;
+
 /// A generic value for the `border-image-slice` property.
 #[derive(
     Clone,
diff --git a/components/style/values/specified/border.rs b/components/style/values/specified/border.rs
index 59f2f7aa284..338b0d18c27 100644
--- a/components/style/values/specified/border.rs
+++ b/components/style/values/specified/border.rs
@@ -183,7 +183,7 @@ impl Parse for BorderImageSideWidth {
         }
 
         if let Ok(len) = input.try(|i| NonNegativeLengthPercentage::parse(context, i)) {
-            return Ok(GenericBorderImageSideWidth::Length(len));
+            return Ok(GenericBorderImageSideWidth::LengthPercentage(len));
         }
 
         let num = NonNegativeNumber::parse(context, input)?;