diff --git a/openhtf/output/callbacks/__init__.py b/openhtf/output/callbacks/__init__.py
index d29ce4531..5a08ef3da 100644
--- a/openhtf/output/callbacks/__init__.py
+++ b/openhtf/output/callbacks/__init__.py
@@ -22,6 +22,8 @@
 
 import collections
 import contextlib
+import os
+import re
 import shutil
 import tempfile
 
@@ -90,6 +92,8 @@ def create_file_name(self, test_record):
     record_dict = data.convert_to_base_types(
         test_record, ignore_keys=('code_info', 'phases', 'log_records'))
     if self._pattern_formattable:
+      record_dict['dut_id'] = self._get_valid_filename(record_dict['dut_id'])
+
       return util.format_string(self.filename_pattern, record_dict)
     else:
       raise ValueError(
@@ -122,3 +126,9 @@ def __call__(self, test_record):
       else:
         raise TypeError('Expected string or iterable but got {}.'.format(
             type(serialized_record)))
+
+  @staticmethod
+  def _get_valid_filename(s):
+      # Reference: https://stackoverflow.com/a/46801075
+      s = str(s).strip().replace(' ', '_')
+      return re.sub(r'(?u)[^-\w.]', '_', s)