diff --git a/smack-core/src/main/java/org/jivesoftware/smack/util/StringUtils.java b/smack-core/src/main/java/org/jivesoftware/smack/util/StringUtils.java
index b6a3a71d6..b632f6847 100644
--- a/smack-core/src/main/java/org/jivesoftware/smack/util/StringUtils.java
+++ b/smack-core/src/main/java/org/jivesoftware/smack/util/StringUtils.java
@@ -261,7 +261,7 @@ public class StringUtils {
         // Create a char buffer to put random letters and numbers in.
         char [] randBuffer = new char[length];
         for (int i=0; i<randBuffer.length; i++) {
-            randBuffer[i] = numbersAndLetters[randGen.nextInt(71)];
+            randBuffer[i] = numbersAndLetters[randGen.nextInt(numbersAndLetters.length)];
         }
         return new String(randBuffer);
     }