diff --git a/xdis/codetype/code310.py b/xdis/codetype/code310.py
index 9f155dd5..4d8fd3fd 100644
--- a/xdis/codetype/code310.py
+++ b/xdis/codetype/code310.py
@@ -206,7 +206,7 @@ def encode_lineno_tab(self):
                 co_linetable += bytearray([0, -127])
                 line_diff -= 127
             if -127 <= line_diff <= 127:
-                co_linetable += bytearray([offset_diff, line_diff % 255])
+                co_linetable += bytearray([offset_diff, line_diff % 256])
 
         self.co_linetable = co_linetable
 
diff --git a/xdis/marsh.py b/xdis/marsh.py
index cc7871ef..f094c01e 100644
--- a/xdis/marsh.py
+++ b/xdis/marsh.py
@@ -358,7 +358,8 @@ def dump_code3(self, x):
         self.dump(x.co_filename)
         self.dump(x.co_name)
         self.w_long(x.co_firstlineno)
-        self.dump(x.co_lnotab)
+        linetable = x.co_linetable if hasattr(x, "co_linetable") else x.co_lnotab
+        self.dump(linetable)
 
     dispatch[Code3] = dump_code3