diff --git a/projects/nat-archive-tool/src/nat/ArchiveController.kiss b/projects/nat-archive-tool/src/nat/ArchiveController.kiss
index a7be3c0e..899a5233 100644
--- a/projects/nat-archive-tool/src/nat/ArchiveController.kiss
+++ b/projects/nat-archive-tool/src/nat/ArchiveController.kiss
@@ -225,7 +225,7 @@
         (doFor e entries
             (if (hasComponent e Images)
                     (withWritableComponents archive e [images Images]
-                        (set images.pinnedImageIndex (max 0 (min images.imageFiles.length (+ increment images.pinnedImageIndex)))))
+                        (set images.pinnedImageIndex (max 0 (min (- images.imageFiles.length 1) (+ increment images.pinnedImageIndex)))))
                 (ui.reportError "Entry $e has no Images component")))
         entries)