--- a/dom/canvas/WebGLTransformFeedback.cpp
+++ b/dom/canvas/WebGLTransformFeedback.cpp
@@ -118,16 +118,28 @@ WebGLTransformFeedback::EndTransformFeed
     if (!mIsActive)
         return mContext->ErrorInvalidOperation("%s: Not active.", funcName);
 
     ////
 
     const auto& gl = mContext->gl;
     gl->fEndTransformFeedback();
 
+    if (gl->WorkAroundDriverBugs()) {
+#ifdef XP_MACOSX
+        // Multi-threaded GL on mac will generate INVALID_OP in some cases for at least
+        // BindBufferBase after an EndTransformFeedback if there is not a flush between
+        // the two.
+        // Single-threaded GL does not have this issue.
+        // This is likely due to not synchronizing client/server state, and erroring in
+        // BindBufferBase because the client thinks we're still in transform feedback.
+        gl->fFlush();
+#endif
+    }
+
     ////
 
     mIsActive = false;
     mIsPaused = false;
 
     ////
 
     mActive_Program->mNumActiveTFOs--;