diff --git a/gnu/packages/engineering.scm b/gnu/packages/engineering.scm
index cdc720d396..36ae757175 100644
--- a/gnu/packages/engineering.scm
+++ b/gnu/packages/engineering.scm
@@ -2472,6 +2472,7 @@ comments.")))
            python-gitpython
            python-matplotlib
            python-pivy
+           python-ply
            python-pyside-2
            python-pyyaml
            python-shiboken-2