diff --git a/src/variety/kurotto.js b/src/variety/kurotto.js
index 86ca126ed..ada7296ac 100644
--- a/src/variety/kurotto.js
+++ b/src/variety/kurotto.js
@@ -83,6 +83,9 @@
 			return this.checkComplete();
 		}
 	},
+	"Cell@island": {
+		minnum: 1
+	},
 	"Board@island": {
 		addExtraInfo: function() {
 			this.islandgraph = this.addInfoList(this.klass.AreaIslandGraph);