diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 544c3f1..2d79031 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -2204,6 +2204,7 @@
         mbmi->palette_mode_info.palette_size[plane];
     if (palette_size_plane > 0) {
       int rows, cols;
+      assert(mbmi->sb_type >= BLOCK_8X8);
       av1_get_block_dimensions(mbmi->sb_type, plane, xd, NULL, NULL, &rows,
                                &cols);
       assert(*tok < tok_end);