diff --git a/pyproject.toml b/pyproject.toml
index da6e1819..9112a5a7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -98,6 +98,10 @@ source = "vcs"
 [tool.hatch.build.hooks.vcs]
 version-file = "_version.py"
 
+[tool.ruff]
+# Mark the directory as a namespace package
+namespace-packages = ["src/swmmanywhere", "src/netcomp"]
+
 [tool.ruff.lint]
 select = ["D", "E", "F", "I"] # pydocstyle, pycodestyle, Pyflakes, isort