diff --git a/gpu/src/ios/GrGLDefaultInterface_iOS.cpp b/gpu/src/ios/GrGLDefaultInterface_iOS.cpp
index 8bc9fc5..7bdbcc7 100644
--- a/gpu/src/ios/GrGLDefaultInterface_iOS.cpp
+++ b/gpu/src/ios/GrGLDefaultInterface_iOS.cpp
@@ -76,6 +76,7 @@
         gDefaultInterface.fMatrixMode = glMatrixMode;
         gDefaultInterface.fPointSize = glPointSize;
         gDefaultInterface.fPixelStorei = glPixelStorei;
+        gDefaultInterface.fReadBuffer = NULL; 
         gDefaultInterface.fReadPixels = glReadPixels;
         gDefaultInterface.fScissor = glScissor;
         gDefaultInterface.fShadeModel = glShadeModel;