diff --git a/docs/requirements.txt b/docs/requirements.txt
index 7295640..150cf8c 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -4,3 +4,4 @@
 # SPDX-License-Identifier: MIT
 
 sphinx>=4.0.0
+pillow>=6.0.0