diff --git a/scripts/app_command.lua b/scripts/app_command.lua
index 50c3b30a4..a96a8b420 100644
--- a/scripts/app_command.lua
+++ b/scripts/app_command.lua
@@ -41,6 +41,21 @@ do -- NewSprite
   assert(s2.colorMode == ColorMode.INDEXED)
 end
 
+do -- ExportSpriteSheet
+  local s = Sprite{ fromFile="sprites/2f-index-3x3.aseprite" }
+  app.command.ExportSpriteSheet {
+    type="horizontal",
+    textureFilename="_test_export_spritesheet1.png",
+    shapePadding=1
+  }
+  local i = Image{ fromFile="_test_export_spritesheet1.png" }
+  expect_img(i,  {
+    11,8,11,21,8,11,11,
+    11,8,11,21,11,8,11,
+    11,8,11,21,11,11,8,
+  })
+end
+
 do -- NewLayer/RemoveLayer
   local s = Sprite(32, 32)
   assert(#s.layers == 1)
diff --git a/sprites/2f-index-3x3.aseprite b/sprites/2f-index-3x3.aseprite
new file mode 100644
index 000000000..55d2ce410
Binary files /dev/null and b/sprites/2f-index-3x3.aseprite differ
diff --git a/sprites/README.md b/sprites/README.md
index d3130d959..14dfd7245 100644
--- a/sprites/README.md
+++ b/sprites/README.md
@@ -23,3 +23,5 @@
   content as in `point4frames.aseprite`. Useful to test if
   `"sourceSize"` is different when two cels from different sprites are
   merged in the same texture atlas.
+* `2f-index-3x3.aseprite`: Indexed, 2 frames, 1 layer, mask color set
+  to index 21.