diff --git a/docs/rtfd-requirements.txt b/docs/rtfd-requirements.txt
index d02c7aa..148102f 100644
--- a/docs/rtfd-requirements.txt
+++ b/docs/rtfd-requirements.txt
@@ -1,4 +1,4 @@
-attrs==19.1.0
+attrs==21.1.0
 cffi==1.12.2
 Sphinx==1.8.4
 sphinx-rtd-theme==0.4.3