diff --git a/src/org/apache/james/mime4j/decoder/Base64InputStream.java b/src/org/apache/james/mime4j/decoder/Base64InputStream.java
index 8bfb33020..2461ed571 100644
--- a/src/org/apache/james/mime4j/decoder/Base64InputStream.java
+++ b/src/org/apache/james/mime4j/decoder/Base64InputStream.java
@@ -38,6 +38,7 @@ public class Base64InputStream extends InputStream {
     private int outIndex = 0;
     private final int[] outputBuffer = new int[3];
     private final byte[] inputBuffer = new byte[4];
+    private boolean done = false;
 
     public Base64InputStream(InputStream s) {
         this.s = s;
@@ -76,12 +77,15 @@ public class Base64InputStream extends InputStream {
         int inCount = 0;
 
         int i;
-        while (true) {
+        // "done" is needed for the two successive '=' at the end
+        while (!done) {
             switch (i = s.read()) {
                 case -1:
                     // No more input - just return, let outputBuffer drain out, and be done
                     return;
                 case '=':
+                    // once we meet the first '=', avoid reading the second '='
+                    done = true;
                     decodeAndEnqueue(inCount);
                     return;
                 default:
diff --git a/tests/src/com/android/email/mail/AddressUnitTests.java b/tests/src/com/android/email/mail/AddressUnitTests.java
index 3ba613ebc..87d1452c3 100644
--- a/tests/src/com/android/email/mail/AddressUnitTests.java
+++ b/tests/src/com/android/email/mail/AddressUnitTests.java
@@ -18,6 +18,7 @@ package com.android.email.mail;
 
 import android.test.AndroidTestCase;
 import android.test.suitebuilder.annotation.SmallTest;
+import org.apache.james.mime4j.decoder.DecoderUtil;
 
 import java.net.URLEncoder;
 import java.io.UnsupportedEncodingException;
@@ -67,6 +68,27 @@ public class AddressUnitTests extends AndroidTestCase {
         mAddress3 = new Address("address3", null);
     }
 
+    // see documentation of DecoderUtil.decodeEncodedWords() for details
+    private String padEncoded(String s) {
+        return "=?UTF-8?B?" + s + "?=";
+    }
+
+    /**
+     * Generate strings of incresing lenght by taking prefix substrings.
+     * For each of them, compare with the decoding of the precomputed base-64 encoding.
+     */
+    public void testBase64Decode() {
+        String testString = "xyza\0\"";
+        String base64Encoded[] = {"", "eA==", "eHk=", "eHl6", "eHl6YQ==", "eHl6YQA=", "eHl6YQAi"};
+        int len = testString.length();
+        for (int i = 1; i <= len; ++i) {
+            String encoded = padEncoded(base64Encoded[i]);
+            String decoded = DecoderUtil.decodeEncodedWords(encoded);
+            String prefix = testString.substring(0, i);
+            assertEquals(""+i, prefix, decoded);
+        }
+    }
+
     /**
      * Test for setAddress().
      */