diff --git a/src/lib.rs b/src/lib.rs
index c3165d0..171a721 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -66,7 +66,7 @@ pub fn add_tiles(game_data: String, image: String, prefix: String) -> String {
                 colour_id: None
             };
 
-            if !game.tiles.contains(&tile) {
+            if tile != bitsy_parser::mock::tile_background() && !game.tiles.contains(&tile) {
                 game.add_tile(tile);
 
                 tile_index += 1;
diff --git a/src/test-resources/expected.bitsy b/src/test-resources/expected.bitsy
index b47d55a..0931f2b 100644
--- a/src/test-resources/expected.bitsy
+++ b/src/test-resources/expected.bitsy
@@ -41,7 +41,7 @@ TIL a
 11111111
 NAME block
 
-TIL 2
+TIL 1
 00011000
 00111000
 00011000
@@ -51,7 +51,7 @@ TIL 2
 00011000
 00111100
 
-TIL 3
+TIL 2
 00111100
 01100110
 01100110
@@ -61,7 +61,7 @@ TIL 3
 01100000
 01111110
 
-TIL 4
+TIL 3
 00111100
 01100110
 01100110