diff --git a/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/StringUtils.java b/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/StringUtils.java
index dbebb9f..557e53f 100644
--- a/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/StringUtils.java
+++ b/oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/StringUtils.java
@@ -35,6 +35,9 @@ public class StringUtils {
      * @return the hex encoded string
      */
     public static String convertBytesToHex(byte[] value) {
+        if (null == value) {
+            throw new IllegalArgumentException();
+        }
         int len = value.length;
         char[] buff = new char[len + len];
         char[] hex = HEX;
@@ -53,6 +56,9 @@ public class StringUtils {
      * @return the byte array
      */
     public static byte[] convertHexToBytes(String s) {
+        if (null == s) {
+            throw new IllegalArgumentException();
+        }
         int len = s.length();
         if (len % 2 != 0) {
             throw new IllegalArgumentException(s);
diff --git a/oak-commons/src/test/java/org/apache/jackrabbit/oak/commons/StringUtilsTest.java b/oak-commons/src/test/java/org/apache/jackrabbit/oak/commons/StringUtilsTest.java
index 5075045..3ce340d 100644
--- a/oak-commons/src/test/java/org/apache/jackrabbit/oak/commons/StringUtilsTest.java
+++ b/oak-commons/src/test/java/org/apache/jackrabbit/oak/commons/StringUtilsTest.java
@@ -30,11 +30,20 @@ public class StringUtilsTest extends TestCase {
         assertEquals("0123", StringUtils.convertBytesToHex(new byte[]{(byte) 0x01, (byte) 0x23}));
         assertEquals("89bd", StringUtils.convertBytesToHex(new byte[]{(byte) 0x89, (byte) 0xbd}));
         assertEquals("face", StringUtils.convertBytesToHex(new byte[]{(byte) 0xfa, (byte) 0xce}));
+        assertEquals("", StringUtils.convertBytesToHex(new byte[]{}));
+        try {
+            StringUtils.convertBytesToHex(null);
+            fail();
+        } catch (IllegalArgumentException e) {
+            // expected
+        }
+
         IOUtilsTest.assertEquals(new byte[]{(byte) 0xfa, (byte) 0xce}, StringUtils.convertHexToBytes("face"));
         IOUtilsTest.assertEquals(new byte[]{(byte) 0xfa, (byte) 0xce}, StringUtils.convertHexToBytes("fAcE"));
         IOUtilsTest.assertEquals(new byte[]{(byte) 0xfa, (byte) 0xce}, StringUtils.convertHexToBytes("FaCe"));
         IOUtilsTest.assertEquals(new byte[]{(byte) 0x09, (byte) 0xaf}, StringUtils.convertHexToBytes("09af"));
-        for (String s : new String[]{"120", "1/", "9:", "fast", "a`", "ag", "0@", "aG"}) {
+        IOUtilsTest.assertEquals(new byte[]{}, StringUtils.convertHexToBytes(""));
+        for (String s : new String[]{"120", "1/", "9:", "fast", "a`", "ag", "0@", "aG", null}) {
             try {
                 StringUtils.convertHexToBytes(s);
                 fail();