diff --git a/docs/rtd-pip-requirements b/docs/rtd-pip-requirements
index 39619185..f9554b00 100644
--- a/docs/rtd-pip-requirements
+++ b/docs/rtd-pip-requirements
@@ -5,4 +5,5 @@ Cython
 astropy-helpers
 astropy
 sphinx-astropy
+sphinx_issues
 -e git+https://github.com/mperrin/poppy.git#egg=poppy