diff --git a/crates/fj-core/src/layers/topology.rs b/crates/fj-core/src/layers/topology.rs
index 05fd02385..4d33c9f9d 100644
--- a/crates/fj-core/src/layers/topology.rs
+++ b/crates/fj-core/src/layers/topology.rs
@@ -15,7 +15,7 @@ impl Layer<Topology> {
     pub fn insert(
         &mut self,
         object: AnyObject<AboutToBeStored>,
-        geometry: &Geometry,
+        geometry: &mut Layer<Geometry>,
         validation: &mut Layer<Validation>,
     ) {
         let mut events = Vec::new();
diff --git a/crates/fj-core/src/operations/insert/insert_trait.rs b/crates/fj-core/src/operations/insert/insert_trait.rs
index 4dd27fe5e..4e1b76eba 100644
--- a/crates/fj-core/src/operations/insert/insert_trait.rs
+++ b/crates/fj-core/src/operations/insert/insert_trait.rs
@@ -42,7 +42,7 @@ macro_rules! impl_insert {
                     let object = (handle.clone(), self).into();
                     core.layers.topology.insert(
                         object,
-                        &core.layers.geometry,
+                        &mut core.layers.geometry,
                         &mut core.layers.validation,
                     );
                     handle