diff --git a/gfx/layers/ipc/LayerTransactionParent.cpp b/gfx/layers/ipc/LayerTransactionParent.cpp
index e4fdc4b0caf..0633a503064 100644
--- a/gfx/layers/ipc/LayerTransactionParent.cpp
+++ b/gfx/layers/ipc/LayerTransactionParent.cpp
@@ -97,12 +97,12 @@ ShadowAfter(const OpInsertAfter& op)
 }
 
 static ShadowLayerParent*
-ShadowContainer(const OpAppendChild& op)
+ShadowContainer(const OpPrependChild& op)
 {
   return cast(op.containerParent());
 }
 static ShadowLayerParent*
-ShadowChild(const OpAppendChild& op)
+ShadowChild(const OpPrependChild& op)
 {
   return cast(op.childLayerParent());
 }
@@ -416,10 +416,10 @@ LayerTransactionParent::RecvUpdate(const InfallibleTArray<Edit>& cset,
       }
       break;
     }
-    case Edit::TOpAppendChild: {
-      MOZ_LAYERS_LOG(("[ParentSide] AppendChild"));
+    case Edit::TOpPrependChild: {
+      MOZ_LAYERS_LOG(("[ParentSide] PrependChild"));
 
-      const OpAppendChild& oac = edit.get_OpAppendChild();
+      const OpPrependChild& oac = edit.get_OpPrependChild();
       Layer* child = ShadowChild(oac)->AsLayer();
       if (!child) {
         return false;
diff --git a/gfx/layers/ipc/LayersMessages.ipdlh b/gfx/layers/ipc/LayersMessages.ipdlh
index 69ad0f86074..13f087f502e 100644
--- a/gfx/layers/ipc/LayersMessages.ipdlh
+++ b/gfx/layers/ipc/LayersMessages.ipdlh
@@ -247,7 +247,7 @@ struct OpSetLayerAttributes {
 // Monkey with the tree structure
 struct OpSetRoot          { PLayer root; };
 struct OpInsertAfter      { PLayer container; PLayer childLayer; PLayer after; };
-struct OpAppendChild      { PLayer container; PLayer childLayer; };
+struct OpPrependChild     { PLayer container; PLayer childLayer; };
 struct OpRemoveChild      { PLayer container; PLayer childLayer; };
 struct OpRepositionChild  { PLayer container; PLayer childLayer; PLayer after; };
 struct OpRaiseToTopChild  { PLayer container; PLayer childLayer; };
@@ -371,7 +371,7 @@ union Edit {
 
   OpSetRoot;
   OpInsertAfter;
-  OpAppendChild;
+  OpPrependChild;
   OpRemoveChild;
   OpRepositionChild;
   OpRaiseToTopChild;
diff --git a/gfx/layers/ipc/ShadowLayers.cpp b/gfx/layers/ipc/ShadowLayers.cpp
index 1cdad1465a6..d7167f44897 100644
--- a/gfx/layers/ipc/ShadowLayers.cpp
+++ b/gfx/layers/ipc/ShadowLayers.cpp
@@ -276,8 +276,8 @@ ShadowLayerForwarder::InsertAfter(ShadowableLayer* aContainer,
                                 nullptr, Shadow(aChild),
                                 nullptr, Shadow(aAfter)));
   else
-    mTxn->AddEdit(OpAppendChild(nullptr, Shadow(aContainer),
-                                nullptr, Shadow(aChild)));
+    mTxn->AddEdit(OpPrependChild(nullptr, Shadow(aContainer),
+                                 nullptr, Shadow(aChild)));
 }
 void
 ShadowLayerForwarder::RemoveChild(ShadowableLayer* aContainer,