--- a/toolkit/components/telemetry/shared_telemetry_utils.py
+++ b/toolkit/components/telemetry/shared_telemetry_utils.py
@@ -8,22 +8,26 @@
 from __future__ import print_function
 
 import re
 import yaml
 import sys
 
 # This is a list of flags that determine which process a measurement is allowed
 # to record from.
+# This map has to contain all historical values as well, since it is used for
+# validating historical files as well as current ones.
 KNOWN_PROCESS_FLAGS = {
     'all': 'All',
     'all_children': 'AllChildren',
     'main': 'Main',
     'content': 'Content',
     'gpu': 'Gpu',
+    # Historical Values
+    'all_childs': 'AllChildren', # Supporting files from before bug 1363725
 }
 
 PROCESS_ENUM_PREFIX = "mozilla::Telemetry::Common::RecordedProcessType::"
 
 
 class ParserError(Exception):
     """Thrown by different probe parsers. Errors are partitioned into
     'immediately fatal' and 'eventually fatal' so that the parser can print