diff --git a/dom/canvas/WebGLContext.cpp b/dom/canvas/WebGLContext.cpp
index a5aa7cc22268..415826221f76 100644
--- a/dom/canvas/WebGLContext.cpp
+++ b/dom/canvas/WebGLContext.cpp
@@ -1034,6 +1034,15 @@ WebGLContext::SetDimensions(int32_t signedWidth, int32_t signedHeight)
         }
     }
 
+    mNeedsFakeNoStencil_UserFBs = false;
+#ifdef MOZ_WIDGET_COCOA
+    if (!nsCocoaFeatures::IsAtLeastVersion(10, 12) &&
+        gl->Vendor() == GLVendor::Intel)
+    {
+        mNeedsFakeNoStencil_UserFBs = true;
+    }
+#endif
+
     mResetLayer = true;
     mOptionsFrozen = true;
 
@@ -2112,7 +2121,8 @@ ScopedDrawCallWrapper::ScopedDrawCallWrapper(WebGLContext& webgl)
     uint8_t driverColorMask = mWebGL.mColorWriteMask;
     bool driverDepthTest    = mWebGL.mDepthTestEnabled;
     bool driverStencilTest  = mWebGL.mStencilTestEnabled;
-    if (!mWebGL.mBoundDrawFramebuffer) {
+    const auto& fb = mWebGL.mBoundDrawFramebuffer;
+    if (!fb) {
         if (mWebGL.mDefaultFB_DrawBuffer0 == LOCAL_GL_NONE) {
             driverColorMask = 0; // Is this well-optimized enough for depth-first
                                  // rendering?
@@ -2121,6 +2131,13 @@ ScopedDrawCallWrapper::ScopedDrawCallWrapper(WebGLContext& webgl)
         }
         driverDepthTest   &= !mWebGL.mNeedsFakeNoDepth;
         driverStencilTest &= !mWebGL.mNeedsFakeNoStencil;
+    } else {
+        if (mWebGL.mNeedsFakeNoStencil_UserFBs &&
+            fb->DepthAttachment().IsDefined() &&
+            !fb->StencilAttachment().IsDefined())
+        {
+            driverStencilTest = false;
+        }
     }
 
     const auto& gl = mWebGL.gl;
diff --git a/dom/canvas/WebGLContext.h b/dom/canvas/WebGLContext.h
index b2f6865cba28..7ec9887a8f4e 100644
--- a/dom/canvas/WebGLContext.h
+++ b/dom/canvas/WebGLContext.h
@@ -1980,6 +1980,7 @@ protected:
     bool mNeedsFakeNoAlpha;
     bool mNeedsFakeNoDepth;
     bool mNeedsFakeNoStencil;
+    bool mNeedsFakeNoStencil_UserFBs;
 
     mutable uint8_t mDriverColorMask;
     bool mDriverDepthTest;
diff --git a/dom/canvas/WebGLContextUtils.cpp b/dom/canvas/WebGLContextUtils.cpp
index 87f2e576bf92..99a03fc1330a 100644
--- a/dom/canvas/WebGLContextUtils.cpp
+++ b/dom/canvas/WebGLContextUtils.cpp
@@ -9,6 +9,7 @@
 #include "GLContext.h"
 #include "jsapi.h"
 #include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/gfx/Logging.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/Sprintf.h"
 #include "nsIDOMEvent.h"
@@ -805,10 +806,17 @@ WebGLContext::AssertCachedGlobalState() const
 
     GLfloat colorClearValue[4] = {0.0f, 0.0f, 0.0f, 0.0f};
     gl->fGetFloatv(LOCAL_GL_COLOR_CLEAR_VALUE, colorClearValue);
-    MOZ_ASSERT(IsCacheCorrect(mColorClearValue[0], colorClearValue[0]) &&
+    const bool ok = IsCacheCorrect(mColorClearValue[0], colorClearValue[0]) &&
                IsCacheCorrect(mColorClearValue[1], colorClearValue[1]) &&
                IsCacheCorrect(mColorClearValue[2], colorClearValue[2]) &&
-               IsCacheCorrect(mColorClearValue[3], colorClearValue[3]));
+               IsCacheCorrect(mColorClearValue[3], colorClearValue[3]);
+    if (!ok) {
+        gfxCriticalNote << mColorClearValue[0] << " - " << colorClearValue[0] << " = " << (mColorClearValue[0] - colorClearValue[0]) << "\n"
+                        << mColorClearValue[1] << " - " << colorClearValue[1] << " = " << (mColorClearValue[1] - colorClearValue[1]) << "\n"
+                        << mColorClearValue[2] << " - " << colorClearValue[2] << " = " << (mColorClearValue[2] - colorClearValue[2]) << "\n"
+                        << mColorClearValue[3] << " - " << colorClearValue[3] << " = " << (mColorClearValue[3] - colorClearValue[3]);
+    }
+    MOZ_ASSERT(ok);
 
     realGLboolean depthWriteMask = 0;
     gl->fGetBooleanv(LOCAL_GL_DEPTH_WRITEMASK, &depthWriteMask);
diff --git a/gfx/gl/MozFramebuffer.cpp b/gfx/gl/MozFramebuffer.cpp
index 9dcbefbdf97e..7d3e4ba346d5 100644
--- a/gfx/gl/MozFramebuffer.cpp
+++ b/gfx/gl/MozFramebuffer.cpp
@@ -53,8 +53,6 @@ MozFramebuffer::Create(GLContext* const gl, const gfx::IntSize& size,
         colorName = gl->CreateTexture();
         const ScopedBindTexture bindTex(gl, colorName);
         gl->TexParams_SetClampNoMips();
-        const ScopedBindPBO bindPBO(gl, LOCAL_GL_PIXEL_UNPACK_BUFFER);
-        gl->fBindBuffer(LOCAL_GL_PIXEL_UNPACK_BUFFER, 0);
         gl->fTexImage2D(colorTarget, 0, LOCAL_GL_RGBA,
                         size.width, size.height, 0,
                         LOCAL_GL_RGBA, LOCAL_GL_UNSIGNED_BYTE, nullptr);