diff --git a/sudoku.py b/sudoku.py
index 6c4ec6c..4376269 100644
--- a/sudoku.py
+++ b/sudoku.py
@@ -203,7 +203,7 @@ class Board(dict):
                 lines.append('\n'.join(box_lines))
                 box_lines = []
                 if x < self.size - 1:
-                    box_dividers = ['-' * (square_size * (2 * self.box_size - 1)) for box in range(self.box_size)]
+                    box_dividers = ['-' * (square_size * self.box_size + square_size)) for box in range(self.box_size)]
                     lines.append('\n{}\n'.format('-+-'.join(box_dividers)))
         return ''.join(lines)