diff --git a/tests/scripts/check_files.py b/tests/scripts/check_files.py
index d20ec2e..33b15ac 100755
--- a/tests/scripts/check_files.py
+++ b/tests/scripts/check_files.py
@@ -285,6 +285,7 @@
         '\u2070\u2071\u2074-\u208E\u2090-\u209C', # Superscripts and Subscripts
         '\u2190-\u21FF', # Arrows
         '\u2200-\u22FF', # Mathematical Symbols
+        '\u2500 \u2514 \u251C' # Box Drawings characters used in markdown trees
     ])
     # Allow any of the characters and ranges above, and anything classified
     # as a word constituent.