diff --git a/src/main/java/org/ntlab/acanthus_server/resources/gallery/LayersRest.java b/src/main/java/org/ntlab/acanthus_server/resources/gallery/LayersRest.java
index c25ab36..88b550c 100644
--- a/src/main/java/org/ntlab/acanthus_server/resources/gallery/LayersRest.java
+++ b/src/main/java/org/ntlab/acanthus_server/resources/gallery/LayersRest.java
@@ -59,10 +59,12 @@
     @Path("/{aid}/pageMap/{pid}/layers/{layerNo}")
     @GET
     @Produces(MediaType.APPLICATION_JSON)
-    public Integer getStrokeSize(@PathParam("aid") Integer aid, @PathParam("pid") Integer pid, @PathParam("layerNo") Integer layerNo) {
+    public Integer getStrokeNo(@PathParam("aid") Integer aid, @PathParam("pid") Integer pid, @PathParam("layerNo") Integer layerNo) {
         var pages = gallery.getAnimationByAid(aid).getPages();
+        var strokes = pages.get(pid).getLayers().get(layerNo).getStrokes();
 
-        return pages.get(pid).getLayers().get(layerNo).getStrokes().size();
+        if (strokes == null) return null;
+        return (strokes.size() - 1);
     }
 
     // _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/