diff --git a/requirements/devel.txt b/requirements/devel.txt
index dabb3286e..72e6d6839 100644
--- a/requirements/devel.txt
+++ b/requirements/devel.txt
@@ -16,6 +16,7 @@ pytest-timeout
 
 sphinx==2.2.0 ; python_version >= '3.0'
 sphinx==1.8.5 ; python_version < '3.0'
+alabaster<0.7.15
 sphinxcontrib-applehelp<1.0.8
 sphinxcontrib-devhelp<1.0.6
 sphinxcontrib-htmlhelp<2.0.5