diff --git a/doc/build.py b/doc/build.py
index 6a38cde2..5d86664a 100755
--- a/doc/build.py
+++ b/doc/build.py
@@ -39,6 +39,7 @@ def build_docs():
   pip_install('michaeljones/breathe',
               '511b0887293e7c6b12310bb61b3659068f48f0f4')
   print(check_output(['pip', '--version']))
+  print(check_output(['pip', 'show', 'sphinx-rtd-theme']))
   print(check_output(['sphinx-build', '--version']))
   print('PATH:', os.environ['PATH'])
   print(check_output(['which', 'sphinx-build']))