diff --git a/doc/en/requirements.txt b/doc/en/requirements.txt
index 4e2b8ce1a..320ee8dcd 100644
--- a/doc/en/requirements.txt
+++ b/doc/en/requirements.txt
@@ -1,4 +1,4 @@
 pygments-pytest>=1.1.0
-sphinx>=1.8.2
+sphinx>=1.8.2,<2.0
 sphinxcontrib-trio
 sphinx-removed-in>=0.1.3