diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index c209a5810..e6ab0018c 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -57,6 +57,7 @@ Christopher Charlier
 Clark Archer
 Clemens Hammacher
 Clement OUDOT
+Clive Brettingham-Moore
 Conor MacNeill
 Craeg Strong
 Craig Cottingham
diff --git a/WHATSNEW b/WHATSNEW
index c70be1c1d..ee5fb45dc 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -72,6 +72,9 @@ Fixed bugs:
  * Depend task does not handle invokeDynamic constant pool entries - java.lang.ClassFormatError: Invalid Constant Pool entry Type 18
    Bugzilla Report 54090
 
+ * Base64Converter not properly handling bytes with MSB set (not masking byte to int conversion)
+   Bugzilla Report 54460
+
 Other changes:
 --------------
 
diff --git a/contributors.xml b/contributors.xml
index f726989c6..91cf53265 100644
--- a/contributors.xml
+++ b/contributors.xml
@@ -250,6 +250,10 @@
     <first>Clement</first>
     <last>OUDOT</last>
   </name>
+  <name>
+    <first>Clive</first>
+    <last>Brettingham-Moore</last>
+  </name>
   <name>
     <first>Conor</first>
     <last>MacNeill</last>
diff --git a/src/main/org/apache/tools/ant/util/Base64Converter.java b/src/main/org/apache/tools/ant/util/Base64Converter.java
index a5f7e5b80..5d60a145f 100644
--- a/src/main/org/apache/tools/ant/util/Base64Converter.java
+++ b/src/main/org/apache/tools/ant/util/Base64Converter.java
@@ -83,7 +83,7 @@ public class Base64Converter {
             // store the octets
             bits24 = (octetString[i++] & BYTE_MASK) << WORD;
             bits24 |= (octetString[i++] & BYTE_MASK) << BYTE;
-            bits24 |= octetString[i++];
+            bits24 |= octetString[i++] & BYTE_MASK;
 
             bits6 = (bits24 & POS_3_MASK) >> POS_3_SHIFT;
             out[outIndex++] = ALPHABET[bits6];
diff --git a/src/tests/junit/org/apache/tools/ant/util/Base64ConverterTest.java b/src/tests/junit/org/apache/tools/ant/util/Base64ConverterTest.java
new file mode 100644
index 000000000..b12d7e266
--- /dev/null
+++ b/src/tests/junit/org/apache/tools/ant/util/Base64ConverterTest.java
@@ -0,0 +1,44 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one or more
+ *  contributor license agreements.  See the NOTICE file distributed with
+ *  this work for additional information regarding copyright ownership.
+ *  The ASF licenses this file to You under the Apache License, Version 2.0
+ *  (the "License"); you may not use this file except in compliance with
+ *  the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ */
+package org.apache.tools.ant.util;
+
+import junit.framework.TestCase;
+
+import java.util.Calendar;
+import java.util.TimeZone;
+
+/**
+ * TestCase for Base64Converter.
+ *
+ */
+public class Base64ConverterTest extends TestCase {
+    public Base64ConverterTest(String s) {
+        super(s);
+    }
+    public void testOneValue() {
+        byte[] mybytes = {0, 0, (byte)0xFF};
+        Base64Converter base64Converter = new Base64Converter();
+        assertEquals("AAD/",base64Converter.encode(mybytes));
+    }
+
+    public void testHelloWorld() {
+        byte[] mybytes = "Hello World".getBytes();
+        Base64Converter base64Converter = new Base64Converter();
+        assertEquals("SGVsbG8gV29ybGQ=", base64Converter.encode(mybytes));
+    }
+}