diff --git a/colcon_python_setup_py/package_augmentation/python_setup_py.py b/colcon_python_setup_py/package_augmentation/python_setup_py.py
index 0010f65..efb8425 100644
--- a/colcon_python_setup_py/package_augmentation/python_setup_py.py
+++ b/colcon_python_setup_py/package_augmentation/python_setup_py.py
@@ -44,7 +44,7 @@ def augment_package(  # noqa: D102
         ]:
             desc.dependencies[dependency_type] = {
                 create_dependency_descriptor(d)
-                for d in config[option_name] or ()}
+                for d in config.get(option_name) or ()}
 
         def getter(env):
             nonlocal setup_py