diff --git a/docs/installation.rst b/docs/installation.rst
index 10125a5d..b1c54559 100644
--- a/docs/installation.rst
+++ b/docs/installation.rst
@@ -190,7 +190,8 @@ of ocrmypdf, and install the following dependencies:
         python3-reportlab \
         qpdf \
         tesseract-ocr \
-        zlib1g
+        zlib1g \
+        unpaper
 
 We will need a newer version of ``pip`` then was available for Ubuntu 18.04: