diff --git a/docs/source/requirements.txt b/docs/source/requirements.txt
index 4b5907f..3a7ffae 100644
--- a/docs/source/requirements.txt
+++ b/docs/source/requirements.txt
@@ -1,4 +1,4 @@
-sphinx>=1.3.0
+sphinx>=1.3.0,!=3.1.0
 sphinx_rtd_theme
 sphinx-prompt
 configparser