diff --git a/agg/include/agg_scanline_u.h b/agg/include/agg_scanline_u.h
index 5a28ed17e..fde48caa3 100644
--- a/agg/include/agg_scanline_u.h
+++ b/agg/include/agg_scanline_u.h
@@ -458,7 +458,7 @@ namespace agg
     class scanline32_u8_am : public scanline32_u8
     {
     public:
-        typedef scanline_u8           base_type;
+        typedef scanline_32_u8           base_type;
         typedef AlphaMask             alpha_mask_type;
         typedef base_type::cover_type cover_type;
         typedef base_type::coord_type coord_type;