diff --git a/gerber/excellon.py b/gerber/excellon.py
index 3fb813f..cdd6d8d 100755
--- a/gerber/excellon.py
+++ b/gerber/excellon.py
@@ -480,6 +480,7 @@ class ExcellonParser(object):
         elif line[:4] == 'FMAT':
             stmt = FormatStmt.from_excellon(line)
             self.statements.append(stmt)
+            self.format = stmt.format_tuple
 
         elif line[:3] == 'G40':
             self.statements.append(CutterCompensationOffStmt())
diff --git a/gerber/excellon_statements.py b/gerber/excellon_statements.py
index 9499c51..e10308a 100644
--- a/gerber/excellon_statements.py
+++ b/gerber/excellon_statements.py
@@ -670,6 +670,10 @@ class FormatStmt(ExcellonStatement):
 
     def to_excellon(self, settings=None):
         return 'FMAT,%d' % self.format
+    
+    @property
+    def format_tuple(self):
+        return (self.format, 6 - self.format)
 
 
 class LinkToolStmt(ExcellonStatement):