diff --git a/gfx/layers/Effects.h b/gfx/layers/Effects.h
index b6f22f21b30..79c3fc24c2a 100644
--- a/gfx/layers/Effects.h
+++ b/gfx/layers/Effects.h
@@ -17,6 +17,7 @@
 #include "mozilla/layers/TextureHost.h"  // for CompositingRenderTarget, etc
 #include "mozilla/mozalloc.h"           // for operator delete, etc
 #include "nscore.h"                     // for nsACString
+#include "mozilla/EnumeratedArray.h"
 
 namespace mozilla {
 namespace layers {
@@ -164,7 +165,8 @@ struct EffectChain
   explicit EffectChain(void* aLayerRef) : mLayerRef(aLayerRef) {}
 
   RefPtr<Effect> mPrimaryEffect;
-  RefPtr<Effect> mSecondaryEffects[size_t(EffectTypes::MAX_SECONDARY)];
+  EnumeratedArray<EffectTypes, EffectTypes::MAX_SECONDARY, RefPtr<Effect>>
+    mSecondaryEffects;
   void* mLayerRef; //!< For LayerScope logging
 };
 
diff --git a/gfx/layers/basic/BasicCompositor.cpp b/gfx/layers/basic/BasicCompositor.cpp
index 0efa2b36100..215e01f626b 100644
--- a/gfx/layers/basic/BasicCompositor.cpp
+++ b/gfx/layers/basic/BasicCompositor.cpp
@@ -291,8 +291,8 @@ BasicCompositor::DrawQuad(const gfx::Rect& aRect,
 
   RefPtr<SourceSurface> sourceMask;
   Matrix maskTransform;
-  if (aEffectChain.mSecondaryEffects[size_t(EffectTypes::MASK)]) {
-    EffectMask *effectMask = static_cast<EffectMask*>(aEffectChain.mSecondaryEffects[size_t(EffectTypes::MASK)].get());
+  if (aEffectChain.mSecondaryEffects[EffectTypes::MASK]) {
+    EffectMask *effectMask = static_cast<EffectMask*>(aEffectChain.mSecondaryEffects[EffectTypes::MASK].get());
     sourceMask = effectMask->mMaskTexture->AsSourceBasic()->GetSurface();
     MOZ_ASSERT(effectMask->mMaskTransform.Is2D(), "How did we end up with a 3D transform here?!");
     MOZ_ASSERT(!effectMask->mIs3D);
diff --git a/gfx/layers/composite/CompositableHost.cpp b/gfx/layers/composite/CompositableHost.cpp
index 62c56b31fcd..40f8b6c6c4c 100644
--- a/gfx/layers/composite/CompositableHost.cpp
+++ b/gfx/layers/composite/CompositableHost.cpp
@@ -158,7 +158,7 @@ CompositableHost::AddMaskEffect(EffectChain& aEffects,
                                              source->GetSize(),
                                              aTransform);
   effect->mIs3D = aIs3D;
-  aEffects.mSecondaryEffects[size_t(EffectTypes::MASK)] = effect;
+  aEffects.mSecondaryEffects[EffectTypes::MASK] = effect;
   return true;
 }
 
diff --git a/gfx/layers/opengl/CompositorOGL.cpp b/gfx/layers/opengl/CompositorOGL.cpp
index 5f751cf71d5..e7fec971212 100644
--- a/gfx/layers/opengl/CompositorOGL.cpp
+++ b/gfx/layers/opengl/CompositorOGL.cpp
@@ -909,8 +909,8 @@ CompositorOGL::DrawQuadInternal(const Rect& aRect,
   EffectMask* effectMask;
   TextureSourceOGL* sourceMask = nullptr;
   gfx::Matrix4x4 maskQuadTransform;
-  if (aEffectChain.mSecondaryEffects[size_t(EffectTypes::MASK)]) {
-    effectMask = static_cast<EffectMask*>(aEffectChain.mSecondaryEffects[size_t(EffectTypes::MASK)].get());
+  if (aEffectChain.mSecondaryEffects[EffectTypes::MASK]) {
+    effectMask = static_cast<EffectMask*>(aEffectChain.mSecondaryEffects[EffectTypes::MASK].get());
     sourceMask = effectMask->mMaskTexture->AsSourceOGL();
 
     // NS_ASSERTION(textureMask->IsAlpha(),