--- a/dom/canvas/WebGLContext.cpp
+++ b/dom/canvas/WebGLContext.cpp
@@ -880,21 +880,21 @@ WebGLContext::SetDimensions(int32_t sign
     disabled |= gfxPlatform::InSafeMode();
 
     if (disabled) {
         const nsLiteralCString text("WebGL is currently disabled.");
         ThrowEvent_WebGLContextCreationError(text);
         return NS_ERROR_FAILURE;
     }
 
-    bool failIfPerfCaveat = mOptions.failIfMajorPerformanceCaveat;
-    if (gfxPrefs::WebGLDisableFailIfMajorPerformanceCaveat())
-        failIfPerfCaveat = false;
+    if (gfxPrefs::WebGLDisableFailIfMajorPerformanceCaveat()) {
+        mOptions.failIfMajorPerformanceCaveat = false;
+    }
 
-    if (failIfPerfCaveat) {
+    if (mOptions.failIfMajorPerformanceCaveat) {
         nsCOMPtr<nsIGfxInfo> gfxInfo = services::GetGfxInfo();
         if (!HasAcceleratedLayers(gfxInfo)) {
             const nsLiteralCString text("failIfMajorPerformanceCaveat: Compositor is not"
                                         " hardware-accelerated.");
             ThrowEvent_WebGLContextCreationError(text);
             return NS_ERROR_FAILURE;
         }
     }
@@ -907,18 +907,26 @@ WebGLContext::SetDimensions(int32_t sign
     nsCString failReason;
     if (!CreateAndInitGL(forceEnabled, &failReason)) {
         const nsPrintfCString text("WebGL creation failed: %s",
                                    failReason.BeginReading());
         ThrowEvent_WebGLContextCreationError(text);
         return NS_ERROR_FAILURE;
     }
     MOZ_ASSERT(gl);
+    MOZ_ASSERT_IF(mOptions.alpha, gl->Caps().alpha);
 
-    MOZ_ASSERT_IF(mOptions.alpha, gl->Caps().alpha);
+    if (mOptions.failIfMajorPerformanceCaveat) {
+        if (gl->IsWARP()) {
+            const nsLiteralCString text("failIfMajorPerformanceCaveat: Driver is not"
+                                        " hardware-accelerated.");
+            ThrowEvent_WebGLContextCreationError(text);
+            return NS_ERROR_FAILURE;
+        }
+    }
 
     if (!ResizeBackbuffer(width, height)) {
         const nsLiteralCString text("Initializing WebGL backbuffer failed.");
         ThrowEvent_WebGLContextCreationError(text);
         return NS_ERROR_FAILURE;
     }
 
 #ifdef DEBUG