diff --git a/src/gallium/drivers/r300/r300_state.c b/src/gallium/drivers/r300/r300_state.c
index 682abcb523b..6130b10602f 100644
--- a/src/gallium/drivers/r300/r300_state.c
+++ b/src/gallium/drivers/r300/r300_state.c
@@ -2076,7 +2076,7 @@ static void r300_set_constant_buffer(struct pipe_context *pipe,
         struct r300_resource *rbuf = r300_resource(cb->buffer);
 
         if (rbuf && rbuf->malloced_buffer)
-            mapped = (uint32_t*)rbuf->malloced_buffer;
+            mapped = (uint32_t*)(rbuf->malloced_buffer + cb->buffer_offset);
         else
             return;
     }