diff --git a/requirements.txt b/requirements.txt
index 3717d0e84..6971bfdc0 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,7 +2,7 @@
 -e .
 alabaster
 Babel
-black
+black; python_version >= '3.6'
 check-manifest
 cov-core
 coverage