diff --git a/pyproject.toml b/pyproject.toml
index 34a8be98eccde68f80a8005aff6785f33903e0e1..49d3a4113c0de450df785f0f2143449ed525e9b6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -35,6 +35,7 @@
         "docopt",
         "scikit-image",
         "matplotlib",
+        "clapp",
         "bob.extension",
         "bob.io.base",
         "bob.bio.base",