diff --git a/components/compositing/compositor.rs b/components/compositing/compositor.rs
index 1d67d9f4b39..e0d11574e0c 100644
--- a/components/compositing/compositor.rs
+++ b/components/compositing/compositor.rs
@@ -12,7 +12,7 @@ use euclid::point::TypedPoint2D;
 use euclid::scale_factor::ScaleFactor;
 use euclid::size::TypedSize2D;
 use gfx_traits::{DevicePixel, LayerPixel, ScrollRootId};
-use gfx_traits::{Epoch, FrameTreeId, FragmentType};
+use gfx_traits::{Epoch, FragmentType};
 use gleam::gl;
 use gleam::gl::types::{GLint, GLsizei};
 use image::{DynamicImage, ImageFormat, RgbImage};
@@ -108,6 +108,15 @@ enum ReadyState {
     ReadyToSaveImage,
 }
 
+#[derive(PartialEq, Eq, Debug, Copy, Clone)]
+struct FrameTreeId(u32);
+
+impl FrameTreeId {
+    pub fn next(&mut self) {
+        self.0 += 1;
+    }
+}
+
 /// NB: Never block on the constellation, because sometimes the constellation blocks on us.
 pub struct IOCompositor<Window: WindowMethods> {
     /// The application window.
diff --git a/components/gfx_traits/lib.rs b/components/gfx_traits/lib.rs
index 72c2b9a0828..c2339f655d9 100644
--- a/components/gfx_traits/lib.rs
+++ b/components/gfx_traits/lib.rs
@@ -88,15 +88,6 @@ impl Epoch {
     }
 }
 
-#[derive(PartialEq, Eq, Debug, Copy, Clone)]
-pub struct FrameTreeId(pub u32);
-
-impl FrameTreeId {
-    pub fn next(&mut self) {
-        self.0 += 1;
-    }
-}
-
 /// A unique ID for every stacking context.
 #[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, HeapSizeOf, PartialEq, Serialize)]
 pub struct StackingContextId(