diff --git a/gfx/2d/Quaternion.h b/gfx/2d/Quaternion.h
index b8c7c854d5e3..8fc060cc3566 100644
--- a/gfx/2d/Quaternion.h
+++ b/gfx/2d/Quaternion.h
@@ -28,7 +28,7 @@ class BaseQuaternion {
   BaseQuaternion(const BaseQuaternion& aOther) {
     x = aOther.x;
     y = aOther.y;
-    z = aOther.y;
+    z = aOther.z;
     w = aOther.w;
   }