diff --git a/docs/source/conf.py b/docs/source/conf.py
index 222b95c9f5..83570574dd 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -155,7 +155,7 @@ html_title = "OpenMC Documentation"
 html_static_path = ['_static']
 
 def setup(app):
-    app.add_stylesheet('theme_overrides.css')
+    app.add_css_file('theme_overrides.css')
 
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
@@ -254,7 +254,7 @@ napoleon_use_ivar = True
 
 intersphinx_mapping = {
     'python': ('https://docs.python.org/3', None),
-    'numpy': ('https://docs.scipy.org/doc/numpy/', None),
+    'numpy': ('https://numpy.org/doc/stable/', None),
     'scipy': ('https://docs.scipy.org/doc/scipy/reference', None),
     'pandas': ('https://pandas.pydata.org/pandas-docs/stable/', None),
     'matplotlib': ('https://matplotlib.org/', None)