diff --git a/java/strings/Kmp.java b/java/strings/Kmp.java
index 0f2b76cf..b48ca69b 100644
--- a/java/strings/Kmp.java
+++ b/java/strings/Kmp.java
@@ -39,7 +39,7 @@ public static int minPeriod(String s) {
         int minPeriod = n - maxBorder;
 
         // check periodicity
-        // if (n % minPeriod != 0) return -1;
+        // if (minPeriod < n && n % minPeriod != 0) return -1;
 
         return minPeriod;
     }