diff --git a/crates/engine/src/commands/edit.rs b/crates/engine/src/commands/edit.rs
index 019d56d1..4bfe6fa7 100644
--- a/crates/engine/src/commands/edit.rs
+++ b/crates/engine/src/commands/edit.rs
@@ -1,6 +1,7 @@
 //! Edit menu.
 
 use effectcraft_color::Label;
+use effectcraft_keyframe::Value as KV;
 use effectcraft_project::{Comp, Expression, ItemKind, Layer, LayerId, LayerSource, TrackMatte};
 use effectcraft_time::Tick;
 use serde_json::{Value, json};
@@ -201,6 +202,21 @@ fn delete(s: &mut Session, p: &Value) -> Result<Value> {
             if l.track_matte.is_some_and(|m| ids.contains(&m.layer)) {
                 l.track_matte = None;
             }
+            // A layer-reference property (an Environment light's Source, an effect's Clone Source,
+            // Back Layer…) must read as None once its layer is gone, in this same history step: a
+            // dead id renders as nothing while the UI shows "None", which means "fall back to the
+            // comp's Environment Layer" (#2153). Keys carry the same value kind as the property.
+            l.props.walk_mut(&mut |p| {
+                let dead = |v: &KV| matches!(v, KV::Layer(Some(id)) if ids.contains(&LayerId(*id)));
+                if dead(&p.value) {
+                    p.value = KV::Layer(None);
+                }
+                for k in &mut p.keys {
+                    if dead(&k.value) {
+                        k.value = KV::Layer(None);
+                    }
+                }
+            });
         }
         st.selected_layers.clear();
         st.selected_props.clear();
diff --git a/crates/engine/src/tests_3d.rs b/crates/engine/src/tests_3d.rs
index cf9773f9..07a48af1 100644
--- a/crates/engine/src/tests_3d.rs
+++ b/crates/engine/src/tests_3d.rs
@@ -131,6 +131,23 @@ fn environment_light_is_listed_and_takes_a_source_layer() {
     assert_eq!(prop(&s, env, "lightOptions/source").as_layer(), None);
 }
 
+/// Deleting the layer a Source points at leaves no dangling id: "None" means the comp's
+/// Environment Layer, and a dead id rendered as nothing at all (#2153).
+#[test]
+fn deleting_a_source_layer_clears_the_reference() {
+    let mut s = session();
+    let sky = s.execute("layer.newSolid", json!({"width": 256, "height": 128, "name": "Sky"})).unwrap()["layer"].as_u64().unwrap();
+    let env = s.execute("layer.newLight", json!({"kind": "Environment", "name": "Env"})).unwrap()["layer"].as_u64().unwrap();
+    s.execute("prop.set", json!({"layer": env, "path": "lightOptions/source", "value": sky})).unwrap();
+    assert_eq!(prop(&s, env, "lightOptions/source").as_layer(), Some(sky));
+    s.execute("edit.clear", json!({"layers": [sky]})).unwrap();
+    assert_eq!(prop(&s, env, "lightOptions/source").as_layer(), None, "the reference goes with the layer");
+    // One history step with the delete, so undo brings both back.
+    s.undo();
+    assert_eq!(prop(&s, env, "lightOptions/source").as_layer(), Some(sky));
+    assert!(s.active_comp().unwrap().layer(effectcraft_project::LayerId(sky)).is_some());
+}
+
 #[test]
 fn three_d_switch_undo_redo() {
     let mut s = session();