diff --git a/src/main/java/com/reandroid/arsc/header/StringPoolHeader.java b/src/main/java/com/reandroid/arsc/header/StringPoolHeader.java
index 1fd21cf..09c41f6 100644
--- a/src/main/java/com/reandroid/arsc/header/StringPoolHeader.java
+++ b/src/main/java/com/reandroid/arsc/header/StringPoolHeader.java
@@ -16,29 +16,34 @@
 package com.reandroid.arsc.header;
 
 import com.reandroid.arsc.chunk.ChunkType;
+import com.reandroid.arsc.item.ByteItem;
 import com.reandroid.arsc.item.IntegerItem;
 import com.reandroid.arsc.item.ShortItem;
 
+
 public class StringPoolHeader extends HeaderBlock{
     private final IntegerItem countStrings;
     private final IntegerItem countStyles;
-    private final ShortItem flagUtf8;
-    private final ShortItem flagSorted;
+    private final ByteItem flagSorted;
+    private final ByteItem flagUtf8;
+    private final ShortItem flagExtra;
     private final IntegerItem startStrings;
     private final IntegerItem startStyles;
     public StringPoolHeader() {
         super(ChunkType.STRING.ID);
         this.countStrings = new IntegerItem();
         this.countStyles = new IntegerItem();
-        this.flagUtf8 = new ShortItem();
-        this.flagSorted = new ShortItem();
+        this.flagSorted = new ByteItem();
+        this.flagUtf8 = new ByteItem();
+        this.flagExtra = new ShortItem();
         this.startStrings = new IntegerItem();
         this.startStyles = new IntegerItem();
 
         addChild(countStrings);
         addChild(countStyles);
-        addChild(flagUtf8);
         addChild(flagSorted);
+        addChild(flagUtf8);
+        addChild(flagExtra);
         addChild(startStrings);
         addChild(startStyles);
     }
@@ -48,18 +53,35 @@ public class StringPoolHeader extends HeaderBlock{
     public IntegerItem getCountStyles() {
         return countStyles;
     }
-    public ShortItem getFlagUtf8() {
+    public ByteItem getFlagUtf8() {
         return flagUtf8;
     }
-    public ShortItem getFlagSorted() {
+    public ByteItem getFlagSorted() {
         return flagSorted;
     }
+    public ShortItem getFlagExtra(){
+        return flagExtra;
+    }
     public IntegerItem getStartStrings() {
         return startStrings;
     }
     public IntegerItem getStartStyles() {
         return startStyles;
     }
+
+    public boolean isUtf8(){
+        return (getFlagUtf8().get() & 0x01) !=0;
+    }
+    public void setUtf8(boolean utf8){
+        getFlagUtf8().set((byte) (utf8 ? 0x01 : 0x00));
+    }
+    public boolean isSorted(){
+        return (getFlagSorted().get() & 0x01) !=0;
+    }
+    public void setSorted(boolean sorted){
+        getFlagSorted().set((byte) (sorted ? 0x01 : 0x00));
+    }
+
     @Override
     public String toString(){
         if(getChunkType()!=ChunkType.STRING){
@@ -68,8 +90,9 @@ public class StringPoolHeader extends HeaderBlock{
         return getClass().getSimpleName()
                 +" {strings="+getCountStrings()
                 +", styles="+getCountStyles()
-                +", utf8="+getFlagUtf8().toHex()
-                +", sorted="+getFlagSorted().toHex()
+                +", utf8="+isUtf8()
+                +", sorted="+isSorted()
+                +", flagExtra="+getFlagExtra().toHex()
                 +", offset-strings="+getStartStrings().get()
                 +", offset-styles="+getStartStyles().get() + '}';
     }
diff --git a/src/main/java/com/reandroid/arsc/pool/StringPool.java b/src/main/java/com/reandroid/arsc/pool/StringPool.java
index a9d490c..61dd028 100755
--- a/src/main/java/com/reandroid/arsc/pool/StringPool.java
+++ b/src/main/java/com/reandroid/arsc/pool/StringPool.java
@@ -244,30 +244,26 @@ package com.reandroid.arsc.pool;
     public void setUtf8(boolean is_utf8){
         setUtf8(is_utf8, true);
     }
-    public final void setSorted(boolean sorted){
-        ShortItem flagSorted = getHeaderBlock().getFlagSorted();
-        if(sorted){
-            flagSorted.set(FLAG_SORTED);
-        }else {
-            flagSorted.set((short)0);
-        }
-    }
     private void setUtf8(boolean is_utf8, boolean updateAll){
-        ShortItem flagUtf8 = getHeaderBlock().getFlagUtf8();
-        boolean old = isUtf8Flag();
-        if(is_utf8){
-            flagUtf8.set(UTF8_FLAG_VALUE);
-        }else {
-            flagUtf8.set((short) 0);
+        StringPoolHeader header = getHeaderBlock();
+        if(is_utf8 == header.isUtf8()){
+            return;
         }
-        if(!updateAll || old == isUtf8Flag()){
+        ByteItem flagUtf8 = header.getFlagUtf8();
+        if(is_utf8){
+            flagUtf8.set((byte) 0x01);
+        }else {
+            flagUtf8.set((byte) 0x00);
+        }
+        if(!updateAll){
             return;
         }
         mArrayStrings.setUtf8(is_utf8);
     }
-    private boolean isUtf8Flag(){
-        return (getHeaderBlock().getFlagUtf8().get() & FLAG_UTF8) !=0;
+    public void setFlagSorted(boolean sorted){
+        getHeaderBlock().setSorted(sorted);
     }
+
     abstract StringArray<T> newInstance(IntegerArray offsets, IntegerItem itemCount, IntegerItem itemStart, boolean is_utf8);
     @Override
     protected void onChunkRefreshed() {
@@ -287,8 +283,9 @@ package com.reandroid.arsc.pool;
 
     @Override
     public void onBlockLoaded(BlockReader reader, Block sender) throws IOException {
-        if(sender == getHeaderBlock().getFlagUtf8()){
-            mArrayStrings.setUtf8(isUtf8Flag());
+        StringPoolHeader header = getHeaderBlock();
+        if(sender == header.getFlagUtf8()){
+            mArrayStrings.setUtf8(header.isUtf8());
         }
     }
     @Override
@@ -310,8 +307,4 @@ package com.reandroid.arsc.pool;
         return s1.compareTo(s2);
     }
 
-    private static final short UTF8_FLAG_VALUE=0x0100;
-
-    private static final short FLAG_UTF8 = 0x0100;
-    private static final short FLAG_SORTED = 0x0100;
 }