diff --git a/pyproject.toml b/pyproject.toml
index e947504cdd..af178b3626 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,6 +45,7 @@ enableTypeIgnoreComments = false
 [tool.ruff]
 exclude = [
     # Submodules.
+    "src/ifcconvert/cityjson",
     "src/ifcopenshell-python/ifcopenshell/express",
     "src/ifcopenshell-python/ifcopenshell/mvd",
     "src/ifcopenshell-python/ifcopenshell/simple_spf",