diff --git a/conf.py b/conf.py
index b9ad9bea..c6860eb9 100644
--- a/conf.py
+++ b/conf.py
@@ -47,7 +47,7 @@
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
 # This pattern also affects html_static_path and html_extra_path.
-exclude_patterns = ['_build','doc/build' '**.ipynb_checkpoints']
+exclude_patterns = ['_build', 'doc/build', '**.ipynb_checkpoints']
 nbsphinx_allow_errors = True
 nbsphinx_execute = 'never'