diff --git a/doc/requirements.txt b/doc/requirements.txt
index 0b9bcf3..71289f8 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,2 +1,3 @@
 exhale
-breathe
\ No newline at end of file
+breathe
+sphinx>=2.1.2
\ No newline at end of file