diff --git a/src/mesa/state_tracker/st_draw.c b/src/mesa/state_tracker/st_draw.c
index f62f2b3a3a3..cc204640eb1 100644
--- a/src/mesa/state_tracker/st_draw.c
+++ b/src/mesa/state_tracker/st_draw.c
@@ -160,6 +160,7 @@ st_draw_vbo(GLcontext *ctx,
          winsys->buffer_reference(winsys, &vbuffer[attr].buffer, stobj->buffer);
          vbuffer[attr].buffer_offset = (unsigned) arrays[0]->Ptr;/* in bytes */
          velement.src_offset = arrays[mesaAttr]->Ptr - arrays[0]->Ptr;
+         assert(velement.src_offset <= 2048); /* 11-bit field */
       }
       else {
          /* attribute data is in user-space memory, not a VBO */