diff --git a/requirements/dev.txt b/requirements/dev.txt
index a43d5a0ebfb1dccc605b0973a21d8cb8f2b5fb4a..a15f53193db42548b50c9adfced31f3d3d65383a 100644
--- a/requirements/dev.txt
+++ b/requirements/dev.txt
@@ -1,4 +1,4 @@
-black
+black==21.6b0
 km3net-testdata>=0.2.19
 matplotlib
 memory_profiler