diff --git a/mobile/android/base/sync/Utils.java b/mobile/android/base/sync/Utils.java
index f622735b8641..e12711b6bc84 100644
--- a/mobile/android/base/sync/Utils.java
+++ b/mobile/android/base/sync/Utils.java
@@ -504,4 +504,20 @@ public class Utils {
     final long duration = endMillis - startMillis;
     return new DecimalFormat("#0.00 seconds").format(((double) duration) / 1000);
   }
-}
+
+  /**
+   * This will take a string containing a UTF-8 representation of a UTF-8
+   * byte array — e.g., "pïgéons1" — and return UTF-8 (e.g., "pïgéons1").
+   *
+   * This is the format produced by desktop Firefox when exchanging credentials
+   * containing non-ASCII characters.
+   */
+  public static String decodeUTF8(final String in) throws UnsupportedEncodingException {
+    final int length = in.length();
+    final byte[] asciiBytes = new byte[length];
+    for (int i = 0; i < length; ++i) {
+      asciiBytes[i] = (byte) in.codePointAt(i);
+    }
+    return new String(asciiBytes, "UTF-8");
+  }
+}
\ No newline at end of file
diff --git a/mobile/android/base/sync/net/BaseResource.java b/mobile/android/base/sync/net/BaseResource.java
index 6abf6d3d0521..9827cf267604 100644
--- a/mobile/android/base/sync/net/BaseResource.java
+++ b/mobile/android/base/sync/net/BaseResource.java
@@ -129,14 +129,22 @@ public class BaseResource implements Resource {
     context.setAttribute(ClientContext.AUTH_CACHE, authCache);
   }
 
+  /**
+   * Return a Header object representing an Authentication header for HTTP Basic.
+   */
+  public static Header getBasicAuthHeader(final String credentials) {
+    Credentials creds = new UsernamePasswordCredentials(credentials);
+
+    // This must be UTF-8 to generate the same Basic Auth headers as desktop for non-ASCII passwords.
+    return BasicScheme.authenticate(creds, "UTF-8", false);
+  }
+
   /**
    * Apply the provided credentials string to the provided request.
    * @param credentials a string, "user:pass".
    */
   private static void applyCredentials(String credentials, HttpUriRequest request, HttpContext context) {
-    Credentials creds = new UsernamePasswordCredentials(credentials);
-    Header header = BasicScheme.authenticate(creds, "US-ASCII", false);
-    request.addHeader(header);
+    request.addHeader(getBasicAuthHeader(credentials));
     Logger.trace(LOG_TAG, "Adding Basic Auth header.");
   }
 
diff --git a/mobile/android/base/sync/setup/activities/SetupSyncActivity.java b/mobile/android/base/sync/setup/activities/SetupSyncActivity.java
index 4a9f1e7cf6a5..857912379fbb 100644
--- a/mobile/android/base/sync/setup/activities/SetupSyncActivity.java
+++ b/mobile/android/base/sync/setup/activities/SetupSyncActivity.java
@@ -4,6 +4,7 @@
 
 package org.mozilla.gecko.sync.setup.activities;
 
+import java.io.UnsupportedEncodingException;
 import java.util.HashMap;
 
 import org.json.simple.JSONObject;
@@ -11,6 +12,7 @@ import org.mozilla.gecko.R;
 import org.mozilla.gecko.sync.GlobalConstants;
 import org.mozilla.gecko.sync.Logger;
 import org.mozilla.gecko.sync.ThreadPool;
+import org.mozilla.gecko.sync.Utils;
 import org.mozilla.gecko.sync.jpake.JPakeClient;
 import org.mozilla.gecko.sync.jpake.JPakeNoActivePairingException;
 import org.mozilla.gecko.sync.setup.Constants;
@@ -392,6 +394,13 @@ public class SetupSyncActivity extends AccountAuthenticatorActivity {
       String syncKey      = (String) jCreds.get(Constants.JSON_KEY_SYNCKEY);
       String serverURL    = (String) jCreds.get(Constants.JSON_KEY_SERVER);
 
+      // The password we get is double-encoded.
+      try {
+        password = Utils.decodeUTF8(password);
+      } catch (UnsupportedEncodingException e) {
+        Logger.warn(LOG_TAG, "Unsupported encoding when decoding UTF-8 ASCII J-PAKE message. Ignoring.");
+      }
+
       final SyncAccountParameters syncAccount = new SyncAccountParameters(mContext, mAccountManager, accountName,
                                                                           syncKey, password, serverURL);
       createAccountOnThread(syncAccount);
diff --git a/src/test/java/org/mozilla/android/sync/net/test/TestCredentialsEndToEnd.java b/src/test/java/org/mozilla/android/sync/net/test/TestCredentialsEndToEnd.java
new file mode 100644
index 000000000000..ea671f5a5c69
--- /dev/null
+++ b/src/test/java/org/mozilla/android/sync/net/test/TestCredentialsEndToEnd.java
@@ -0,0 +1,70 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+package org.mozilla.android.sync.net.test;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+
+import org.json.simple.parser.ParseException;
+import org.junit.Test;
+import org.mozilla.gecko.sync.ExtendedJSONObject;
+import org.mozilla.gecko.sync.NonObjectJSONException;
+import org.mozilla.gecko.sync.Utils;
+import org.mozilla.gecko.sync.net.BaseResource;
+
+import ch.boye.httpclientandroidlib.Header;
+
+/**
+ * Test the transfer of a UTF-8 string from desktop, and ensure that it results in the
+ * correct hashed Basic Auth header.
+ */
+public class TestCredentialsEndToEnd {
+
+  public static final String REAL_PASSWORD         = "pïgéons1";
+  public static final String USERNAME              = "utvm3mk6hnngiir2sp4jsxf2uvoycrv6";
+  public static final String DESKTOP_PASSWORD_JSON = "{\"password\":\"pïgéons1\"}";
+  public static final String BTOA_PASSWORD         = "cMOvZ8Opb25zMQ==";
+  public static final int    DESKTOP_ASSERTED_SIZE = 10;
+  public static final String DESKTOP_BASIC_AUTH    = "Basic dXR2bTNtazZobm5naWlyMnNwNGpzeGYydXZveWNydjY6cMOvZ8Opb25zMQ==";
+
+  private String getCreds(String password) {
+    Header authenticate = BaseResource.getBasicAuthHeader(USERNAME + ":" + password);
+    return authenticate.getValue();
+  }
+
+  @SuppressWarnings("static-method")
+  @Test
+  public void testUTF8() throws UnsupportedEncodingException {
+    final String in  = "pïgéons1";
+    final String out = "pïgéons1";
+    assertEquals(out, Utils.decodeUTF8(in));
+  }
+
+  @Test
+  public void testAuthHeaderFromPassword() throws NonObjectJSONException, IOException, ParseException {
+    final ExtendedJSONObject parsed = new ExtendedJSONObject(DESKTOP_PASSWORD_JSON);
+
+    final String password = parsed.getString("password");
+    final String decoded = Utils.decodeUTF8(password);
+
+    final byte[] expectedBytes = Utils.decodeBase64(BTOA_PASSWORD);
+    final String expected = new String(expectedBytes, "UTF-8");
+
+    assertEquals(DESKTOP_ASSERTED_SIZE, password.length());
+    assertEquals(expected, decoded);
+
+    System.out.println("Retrieved password: " + password);
+    System.out.println("Expected password:  " + expected);
+    System.out.println("Rescued password:   " + decoded);
+
+    assertEquals(getCreds(expected), getCreds(decoded));
+    assertEquals(getCreds(decoded), DESKTOP_BASIC_AUTH);
+  }
+
+  // Note that we do *not* have a test for the J-PAKE setup process
+  // (SetupSyncActivity) that actually stores credentials and requires
+  // decodeUTF8. This will have to suffice.
+}