diff --git a/apktool-lib/src/main/java/brut/androlib/res/AndrolibResources.java b/apktool-lib/src/main/java/brut/androlib/res/AndrolibResources.java
index 515416d6..a4a13601 100644
--- a/apktool-lib/src/main/java/brut/androlib/res/AndrolibResources.java
+++ b/apktool-lib/src/main/java/brut/androlib/res/AndrolibResources.java
@@ -244,7 +244,7 @@ final public class AndrolibResources {
                 , "    ");
         serial.setProperty(ExtXmlSerializer.PROPERTY_SERIALIZER_LINE_SEPARATOR,
             System.getProperty("line.separator"));
-        serial.setProperty(ExtMXSerializer.PROPERTY_DEFAULT_ENCODING, "UTF-8");
+        serial.setProperty(ExtMXSerializer.PROPERTY_DEFAULT_ENCODING, "utf-8");
         return serial;
     }
 
diff --git a/apktool-lib/src/test/resources/brut/apktool/testapp/AndroidManifest.xml b/apktool-lib/src/test/resources/brut/apktool/testapp/AndroidManifest.xml
index c6a6a653..d79f6186 100644
--- a/apktool-lib/src/test/resources/brut/apktool/testapp/AndroidManifest.xml
+++ b/apktool-lib/src/test/resources/brut/apktool/testapp/AndroidManifest.xml
@@ -1,3 +1,3 @@
-<?xml version="1.0" encoding="UTF-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <manifest android:versionCode="1" android:versionName="1.0" package="brut.apktool.testapp"
   xmlns:android="http://schemas.android.com/apk/res/android" />
diff --git a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc001/strings.xml b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc001/strings.xml
index 5e9db678..f4e44dc0 100644
--- a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc001/strings.xml
+++ b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc001/strings.xml
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="UTF-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <resources>
     <string name="test_literal1"></string>
     <string name="test_literal2">Lorem ipsum...</string>
diff --git a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc002/strings.xml b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc002/strings.xml
index e0ebc5d9..a3521932 100644
--- a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc002/strings.xml
+++ b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc002/strings.xml
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="UTF-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <resources>
     <string name="test_reference1">@android:string/ok</string>
 </resources>
diff --git a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/bools.xml b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/bools.xml
index d3788db9..cf6de945 100644
--- a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/bools.xml
+++ b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/bools.xml
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="UTF-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <resources>
     <item type="bool" name="test_crossType_str2bool">TEST</item>
 </resources>
diff --git a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/integers.xml b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/integers.xml
index 7cd49838..2540c7b4 100644
--- a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/integers.xml
+++ b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/integers.xml
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="UTF-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <resources>
     <item type="integer" name="test_crossType_str2int">TEST</item>
 </resources>
diff --git a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/strings.xml b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/strings.xml
index f72478b8..b97cd2f7 100644
--- a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/strings.xml
+++ b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values-mcc003/strings.xml
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="UTF-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <resources>
     <item type="string" name="test_crossType_bool2str">true</item>
     <item type="string" name="test_crossType_int2str">5</item>
diff --git a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values/strings.xml b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values/strings.xml
index a8cb8262..00ec9a40 100644
--- a/apktool-lib/src/test/resources/brut/apktool/testapp/res/values/strings.xml
+++ b/apktool-lib/src/test/resources/brut/apktool/testapp/res/values/strings.xml
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="UTF-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <resources>
     <string name="test1" />
 </resources>