diff --git a/requirements-doc.txt b/requirements-doc.txt
index 383cf836..99de59de 100644
--- a/requirements-doc.txt
+++ b/requirements-doc.txt
@@ -1,7 +1,7 @@
 # Packages for read the docs
 # Using single requirments for docs, see:
 # https://github.com/rtfd/readthedocs.org/issues/2070
-sphinx_rtd_theme
+sphinx_rtd_theme == 1.3.0
 pypsa == 0.20.1
 numpydoc
 sqlalchemy
@@ -9,4 +9,5 @@ geoalchemy2
 matplotlib
 nbsphinx
 saio
-pyomo != 6.4.3
\ No newline at end of file
+pyomo != 6.4.3
+sphinx