diff --git a/hed/models/hed_string.py b/hed/models/hed_string.py
index 328316868..fe559689c 100644
--- a/hed/models/hed_string.py
+++ b/hed/models/hed_string.py
@@ -37,6 +37,7 @@ def __init__(self, hed_string, hed_schema, def_dict=None, _contents=None):
         super().__init__(hed_string, contents=contents, startpos=0, endpos=len(hed_string))
         self._schema = hed_schema
         self._from_strings = None
+        self._def_dict = def_dict
 
     @classmethod
     def from_hed_strings(cls, hed_strings):
@@ -55,7 +56,8 @@ def from_hed_strings(cls, hed_strings):
         hed_string = ",".join([group._hed_string for group in hed_strings])
         contents = [child for sub_string in hed_strings for child in sub_string.children]
         first_schema = hed_strings[0]._schema
-        new_string.__init__(hed_string=hed_string, _contents=contents, hed_schema=first_schema)
+        first_dict = hed_strings[0]._def_dict
+        new_string.__init__(hed_string=hed_string, _contents=contents, hed_schema=first_schema, def_dict=first_dict)
         new_string._from_strings = hed_strings
         return new_string
 
@@ -344,7 +346,7 @@ def validate(self, allow_placeholders=True, error_handler=None):
         """
         from hed.validator import HedValidator
 
-        validator = HedValidator(self._schema)
+        validator = HedValidator(self._schema, def_dicts=self._def_dict)
         return validator.validate(self, allow_placeholders=allow_placeholders, error_handler=error_handler)
 
     def find_top_level_tags(self, anchor_tags, include_groups=2):