diff --git a/docs/conf.py b/docs/conf.py
index 0fa840b4885..cf5c1c1d02f 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -135,7 +135,7 @@
 ]
 
 nbsphinx_prolog = r"""
-{% set docname = 'docs/' + env.doc2path(env.docname, base=None) %}
+{% set docname = 'docs/' + env.doc2path(str(env.docname), base=None) %}
 .. raw:: html
     
     <style>