diff --git a/_server/editor.js b/_server/editor.js
index 1a1b100b..bc5a6f08 100644
--- a/_server/editor.js
+++ b/_server/editor.js
@@ -481,7 +481,8 @@ editor.prototype.updateLastUsedMap = function () {
     ctx.lineWidth = 4;
     for (var i = 0; i < lastUsed.length; ++i) {
         try {
-            var x = i % core.__SIZE__, y = parseInt(i / core.__SIZE__);
+            var per_row = core.__SIZE__ - 1;
+            var x = i % per_row, y = parseInt(i / per_row);
             var info = lastUsed[i];
             if (!info || !info.images) continue;
             if (info.isTile && core.material.images.tilesets[info.images]) {
diff --git a/_server/editor_mappanel.js b/_server/editor_mappanel.js
index ae10844e..e7e5a30f 100644
--- a/_server/editor_mappanel.js
+++ b/_server/editor_mappanel.js
@@ -852,7 +852,8 @@ editor_mappanel_wrapper = function (editor) {
         var px = scrollLeft + e.clientX - editor.dom.mid2.offsetLeft - editor.dom.lastUsedDiv.offsetLeft + editor.dom.lastUsedDiv.scrollLeft,
             py = scrollTop + e.clientY - editor.dom.mid2.offsetTop - editor.dom.lastUsedDiv.offsetTop + editor.dom.lastUsedDiv.scrollTop;
         var x = parseInt(px / 32), y = parseInt(py / 32);
-        var index = x + core.__SIZE__ * y;
+        if (x == core.__SIZE__ - 1) return false;
+        var index = x + (core.__SIZE__ - 1) * y;
         if (index >= editor.uivalues.lastUsed.length) return;
         var lastUsed = editor.uivalues.lastUsed.sort(function (a, b) {
             if ((a.istop || 0) != (b.istop || 0)) return (b.istop || 0) - (a.istop || 0);