diff --git a/DokoMemo/dokomemo.js b/DokoMemo/dokomemo.js
index 3fb991d..63c96b6 100644
--- a/DokoMemo/dokomemo.js
+++ b/DokoMemo/dokomemo.js
@@ -140,6 +140,10 @@
     }
     function resetMarkers() {
 	let m;
+	if (markers.length==0) {
+	    dispInfo("まだ何一つ覚えていない...");
+	    return;
+	}
 	while (m=markers.shift()) {
 	    rmMarker(m);
 	}