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 82e75f8b7..a3d7ad096 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
@@ -283,8 +283,8 @@ public class StringUtils {
     }
 
     public static String randomString(final int length, Random random) {
-        if (length < 1) {
-            return null;
+        if (length == 0) {
+            return "";
         }
 
         byte[] randomBytes = new byte[length];
diff --git a/smack-core/src/test/java/org/jivesoftware/smack/util/StringUtilsTest.java b/smack-core/src/test/java/org/jivesoftware/smack/util/StringUtilsTest.java
index 0cff5a730..7679a118e 100644
--- a/smack-core/src/test/java/org/jivesoftware/smack/util/StringUtilsTest.java
+++ b/smack-core/src/test/java/org/jivesoftware/smack/util/StringUtilsTest.java
@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2003-2007 Jive Software.
+ * Copyright 2003-2007 Jive Software, 2019 Florian Schmaus.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -88,13 +88,7 @@ public class StringUtilsTest  {
 
     @Test
     public void testRandomString() {
-        // Boundary test
-        String result = StringUtils.randomString(-1);
-        assertNull(result);
-
-        // Zero length string test
-        result = StringUtils.randomString(0);
-        assertNull(result);
+        String result;
 
         // Test various lengths - make sure the same length is returned
         result = StringUtils.randomString(4);
@@ -104,4 +98,17 @@ public class StringUtilsTest  {
         result = StringUtils.randomString(128);
         assertTrue(result.length() == 128);
     }
+
+    @Test(expected = NegativeArraySizeException.class)
+    public void testNegativeArraySizeException() {
+        // Boundary test
+        StringUtils.randomString(-1);
+    }
+
+    @Test
+    public void testZeroLengthRandomString() {
+        // Zero length string test
+        String result = StringUtils.randomString(0);
+        assertEquals("", result);
+    }
 }