diff --git a/components/style/values/generics/mod.rs b/components/style/values/generics/mod.rs
index c0a3823f3b0..43cf722fb7e 100644
--- a/components/style/values/generics/mod.rs
+++ b/components/style/values/generics/mod.rs
@@ -26,6 +26,12 @@ impl<L> HasViewportPercentage for BorderRadiusSize<L> {
     fn has_viewport_percentage(&self) -> bool { false }
 }
 
+impl<L: Clone> From<L> for BorderRadiusSize<L> {
+    fn from(other: L) -> Self {
+        Self::new(other.clone(), other)
+    }
+}
+
 impl<L> BorderRadiusSize<L> {
     #[inline]
     /// Create a new `BorderRadiusSize` for an area of given width and height.
diff --git a/ports/geckolib/glue.rs b/ports/geckolib/glue.rs
index 906358fd48c..d97fca4ab25 100644
--- a/ports/geckolib/glue.rs
+++ b/ports/geckolib/glue.rs
@@ -1446,18 +1446,14 @@ pub extern "C" fn Servo_MediaList_DeleteMedium(list: RawServoMediaListBorrowed,
 }
 
 macro_rules! get_longhand_from_id {
-    ($id:expr, $retval:expr) => {
+    ($id:expr) => {
         match PropertyId::from_nscsspropertyid($id) {
             Ok(PropertyId::Longhand(long)) => long,
             _ => {
-                error!("stylo: unknown presentation property with id {:?}", $id);
-                return $retval
+                panic!("stylo: unknown presentation property with id {:?}", $id);
             }
         }
     };
-    ($id:expr) => {
-        get_longhand_from_id!($id, ())
-    }
 }
 
 macro_rules! match_wrap_declared {
@@ -1467,8 +1463,7 @@ macro_rules! match_wrap_declared {
                 LonghandId::$property => PropertyDeclaration::$property($inner),
             )*
             _ => {
-                error!("stylo: Don't know how to handle presentation property {:?}", $longhand);
-                return
+                panic!("stylo: Don't know how to handle presentation property {:?}", $longhand);
             }
         }
     )
@@ -1480,7 +1475,7 @@ pub extern "C" fn Servo_DeclarationBlock_PropertyIsSet(declarations:
                                                        property: nsCSSPropertyID)
         -> bool {
     use style::properties::PropertyDeclarationId;
-    let long = get_longhand_from_id!(property, false);
+    let long = get_longhand_from_id!(property);
     read_locked_arc(declarations, |decls: &PropertyDeclarationBlock| {
         decls.get(PropertyDeclarationId::Longhand(long)).is_some()
     })
@@ -1575,7 +1570,7 @@ pub extern "C" fn Servo_DeclarationBlock_SetPixelValue(declarations:
     use style::properties::{PropertyDeclaration, LonghandId};
     use style::properties::longhands::border_spacing::SpecifiedValue as BorderSpacing;
     use style::values::specified::BorderWidth;
-    use style::values::specified::length::NoCalcLength;
+    use style::values::specified::length::{NoCalcLength, LengthOrPercentage};
 
     let long = get_longhand_from_id!(property);
     let nocalc = NoCalcLength::from_px(value);
@@ -1601,6 +1596,10 @@ pub extern "C" fn Servo_DeclarationBlock_SetPixelValue(declarations:
                 vertical: None,
             }
         ),
+        BorderTopLeftRadius => Box::new(LengthOrPercentage::from(nocalc).into()),
+        BorderTopRightRadius => Box::new(LengthOrPercentage::from(nocalc).into()),
+        BorderBottomLeftRadius => Box::new(LengthOrPercentage::from(nocalc).into()),
+        BorderBottomRightRadius => Box::new(LengthOrPercentage::from(nocalc).into()),
     };
     write_locked_arc(declarations, |decls: &mut PropertyDeclarationBlock| {
         decls.push(prop, Importance::Normal);