diff --git a/cohorts/cohort.py b/cohorts/cohort.py
index 8c7a5e6..8632627 100644
--- a/cohorts/cohort.py
+++ b/cohorts/cohort.py
@@ -506,6 +506,7 @@ def load_variants(self, patients=None, filter_fn=None, **kwargs):
     def _hash_filter_fn(self, filter_fn, **kwargs):
         if filter_fn is None:
             return 'filter-none'
+        filter_fn_name = filter_fn.__name__
         logger.debug('Computing hash for filter_fn: {} with kwargs {}'.format(filter_fn_name, str(dict(**kwargs))))
         # function source code
         fn_source = str(dill.source.getsource(filter_fn))
diff --git a/pylintrc b/pylintrc
index cef3c9f..68094bf 100644
--- a/pylintrc
+++ b/pylintrc
@@ -2,4 +2,4 @@
 # Without ignoring this, we get errors like:
 # E:249,20: Module 'numpy' has no 'nan' member (no-member)
 ignored-modules = numpy, inspect
-ignored-classes = DataFrameHolder, TextFileReader, tuple, list, zip, izip
+ignored-classes = DataFrameHolder, TextFileReader, tuple, list, zip, izip, str