diff --git a/tpl/macro.twig b/tpl/macro.twig
index 4c5afb2..f555852 100644
--- a/tpl/macro.twig
+++ b/tpl/macro.twig
@@ -85,8 +85,7 @@ public {{_self.struct_type(o)}} {{o.name}} {{_self.base_struct_class(o)}}
   public {{_self.override(o)}} int getWritableFieldsCount() 
   {
 {%~ if has_token(o, 'bitfields') ~%}
-    return Meta.GetDirtyFieldsCount(fields_mask, fields_count: {{fields_count(o)}}) 
-    + Meta.MASK_HEADER_FIELDS_COUNT;
+    return fields_mask.GetDirtyFieldsCount() + Meta.MASK_HEADER_FIELDS_COUNT;
 {% else %}
     return {{fields_count(o)}};
 {%- endif ~%}
@@ -118,7 +117,7 @@ public {{_self.struct_type(o)}} {{o.name}} {{_self.base_struct_class(o)}}
 
 {%- macro decl_struct_fields(o) -%}
 {%- if has_token(o, 'bitfields') ~%}
-public long fields_mask;
+public FieldsMask fields_mask;
 {%- endif -%}
 {%- for f in o.fields ~%}
 {{_self.decl_struct_field(o, f)}}
@@ -146,7 +145,7 @@ base.reset();
 {{var_reset(f.name, f.type, token_or(f, 'default', null))}}
 {%- endfor -%}
 {%- if has_token(o, 'bitfields') ~%} 
-fields_mask = 0L;
+ResetFieldMask();
 {%- endif -%}
 {% endmacro %}
 
@@ -236,7 +235,7 @@ base.syncFields(ctx);
 
   public void ResetFieldMask()
   {
-    fields_mask = 0L;
+    fields_mask = FieldsMask.MakeClean(fields_amount: {{fields_count(o)}});
   }
 
   public void SetPrimaryFieldsChanged()
@@ -250,27 +249,27 @@ base.syncFields(ctx);
 
   public void SetDirtyMask()
   {
-    fields_mask = ~0L;
+    fields_mask = FieldsMask.MakeDirty(fields_amount: {{fields_count(o)}});
   }
 
-    public void SetDirtyMaskDeep()
-    {
-      SetDirtyMask();
+  public void SetDirtyMaskDeep()
+  {
+    SetDirtyMask();
 {%- for f in o.fields ~%}
 {%- if f.type is instanceof('\\mtgMetaStruct') and has_token(f.type, 'bitfields') ~%}
-        {{f.name}}.SetDirtyMaskDeep();
+    {{f.name}}.SetDirtyMaskDeep();
 {%- elseif f.type is instanceof('\\mtgArrType') and f.type.value is instanceof('\\mtgMetaStruct') and has_token(f.type.value, "bitfields") ~%}
+    {
+      for(int i=0;i<{{f.name}}.Count;++i) 
       {
-        for(int i=0;i<{{f.name}}.Count;++i) 
-        {
-          var __tmp = {{f.name}}[i];
-          __tmp.SetDirtyMaskDeep();
-          {{f.name}}[i] = __tmp;
-        }
+        var __tmp = {{f.name}}[i];
+        __tmp.SetDirtyMaskDeep();
+        {{f.name}}[i] = __tmp;
       }
+    }
 {%- endif -%}
 {%- endfor ~%}
-    }
+  }
 
 {%- endmacro -%}