diff --git a/nnfwtbn/plot.py b/nnfwtbn/plot.py
index e15344e65873ab2b169b31872df7e74c82e8d5ac..1f9591c373bec5b017c76f8d40127e92018b541e 100644
--- a/nnfwtbn/plot.py
+++ b/nnfwtbn/plot.py
@@ -38,9 +38,9 @@ def _type_to_histtype(type):
     """
     Returns the matplotlib histogram type for a given process plotting type.
 
-    >>> type_to_histtype("fill")
+    >>> _type_to_histtype("fill")
     'stepfilled'
-    >>> type_to_histtype("line")
+    >>> _type_to_histtype("line")
     'step'
     """
     type_map = {"fill": "stepfilled", "line": "step"}