--- a/dom/canvas/WebGLContext.cpp
+++ b/dom/canvas/WebGLContext.cpp
@@ -1954,22 +1954,22 @@ WebGLContext::GetSurfaceSnapshot(bool* o
     {
         ScopedBindFramebuffer autoFB(gl, 0);
         ClearBackbufferIfNeeded();
 
         // Save, override, then restore glReadBuffer.
         const GLenum readBufferMode = gl->Screen()->GetReadBufferMode();
 
         if (readBufferMode != LOCAL_GL_BACK) {
-            gl->fReadBuffer(LOCAL_GL_BACK);
+            gl->Screen()->SetReadBuffer(LOCAL_GL_BACK);
         }
         ReadPixelsIntoDataSurface(gl, surf);
 
         if (readBufferMode != LOCAL_GL_BACK) {
-            gl->fReadBuffer(readBufferMode);
+            gl->Screen()->SetReadBuffer(readBufferMode);
         }
     }
 
     if (out_premultAlpha) {
         *out_premultAlpha = true;
     }
     bool srcPremultAlpha = mOptions.premultipliedAlpha;
     if (!srcPremultAlpha) {