use _mesa_unmap_buffer by default
diff --git a/src/mesa/drivers/common/driverfuncs.c b/src/mesa/drivers/common/driverfuncs.c
index 643a8c1..df5f6ac 100644
--- a/src/mesa/drivers/common/driverfuncs.c
+++ b/src/mesa/drivers/common/driverfuncs.c
@@ -1,6 +1,6 @@
 /*
  * Mesa 3-D graphics library
- * Version:  6.1
+ * Version:  6.3
  *
  * Copyright (C) 1999-2004  Brian Paul   All Rights Reserved.
  *
@@ -187,7 +187,7 @@
    driver->BufferSubData = _mesa_buffer_subdata;
    driver->GetBufferSubData = _mesa_buffer_get_subdata;
    driver->MapBuffer = _mesa_buffer_map;
-   driver->UnmapBuffer = NULL;
+   driver->UnmapBuffer = _mesa_buffer_unmap;
 #endif
 
    /* T&L stuff */