diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index 9dbf0ec3852..fd1307f4e17 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -76,8 +76,9 @@ pub use self::page::{PageName, PageSize, PageSizeOrientation, PaperSize};
 pub use self::percentage::{NonNegativePercentage, Percentage};
 pub use self::position::AspectRatio;
 pub use self::position::{
-    GridAutoFlow, GridTemplateAreas, MasonryAutoFlow, Position, PositionOrAuto,
+    GridAutoFlow, GridTemplateAreas, Position, PositionOrAuto,
 };
+pub use self::position::{MasonryAutoFlow, MasonryPlacement, MasonryItemOrder};
 pub use self::position::{PositionComponent, ZIndex};
 pub use self::ratio::Ratio;
 pub use self::rect::NonNegativeLengthOrNumberRect;
diff --git a/components/style/values/specified/position.rs b/components/style/values/specified/position.rs
index b40460cdcd7..e447c52f0c4 100644
--- a/components/style/values/specified/position.rs
+++ b/components/style/values/specified/position.rs
@@ -391,6 +391,7 @@ bitflags! {
     }
 }
 
+#[repr(u8)]
 #[derive(
     Clone,
     Copy,
@@ -412,6 +413,7 @@ pub enum MasonryPlacement {
     Next,
 }
 
+#[repr(u8)]
 #[derive(
     Clone,
     Copy,
@@ -446,6 +448,7 @@ pub enum MasonryItemOrder {
     ToResolvedValue,
     ToShmem,
 )]
+#[repr(C)]
 /// Controls how the Masonry layout algorithm works
 /// specifying exactly how auto-placed items get flowed in the masonry axis.
 pub struct MasonryAutoFlow {
@@ -525,37 +528,6 @@ impl Parse for MasonryAutoFlow {
     }
 }
 
-#[cfg(feature = "gecko")]
-impl From<u8> for MasonryAutoFlow {
-    fn from(bits: u8) -> MasonryAutoFlow {
-        use crate::gecko_bindings::structs;
-        let mut value = MasonryAutoFlow::initial();
-        if bits & structs::NS_STYLE_MASONRY_PLACEMENT_PACK as u8 == 0 {
-            value.placement = MasonryPlacement::Next;
-        }
-        if bits & structs::NS_STYLE_MASONRY_ORDER_DEFINITE_FIRST as u8 == 0 {
-            value.order = MasonryItemOrder::Ordered;
-        }
-        value
-    }
-}
-
-#[cfg(feature = "gecko")]
-impl From<MasonryAutoFlow> for u8 {
-    fn from(v: MasonryAutoFlow) -> u8 {
-        use crate::gecko_bindings::structs;
-
-        let mut result: u8 = 0;
-        if v.placement == MasonryPlacement::Pack {
-            result |= structs::NS_STYLE_MASONRY_PLACEMENT_PACK as u8;
-        }
-        if v.order == MasonryItemOrder::DefiniteFirst {
-            result |= structs::NS_STYLE_MASONRY_ORDER_DEFINITE_FIRST as u8;
-        }
-        result
-    }
-}
-
 // TODO: Can be derived with some care.
 impl Parse for GridAutoFlow {
     /// [ row | column ] || dense