--- a/toolkit/components/telemetry/histogram_tools.py
+++ b/toolkit/components/telemetry/histogram_tools.py
@@ -434,16 +434,18 @@ associated with the histogram.  Returns 
         for key, key_type in type_checked_list_fields.iteritems():
             if key not in definition:
                 continue
             if not all(isinstance(x, key_type) for x in definition[key]):
                 raise ParserError('All values for list "{0}" in histogram "{1}" should be of type'
                                   ' {2}.'.format(key, name, nice_type_name(key_type)))
 
     def check_keys(self, name, definition, allowed_keys):
+        if not self._strict_type_checks:
+            return
         for key in definition.iterkeys():
             if key not in allowed_keys:
                 raise ParserError('Key "%s" is not allowed for histogram "%s".' % (key, name))
 
     def set_bucket_parameters(self, low, high, n_buckets):
         self._low = low
         self._high = high
         self._n_buckets = n_buckets