diff --git a/tamer/src/asg/graph.rs b/tamer/src/asg/graph.rs
index c24520c2..8a3ae72b 100644
--- a/tamer/src/asg/graph.rs
+++ b/tamer/src/asg/graph.rs
@@ -430,12 +430,13 @@ pub trait AsgObjectMut: ObjectKind {
     ///     and the commit cannot fail.
     /// If [`Err`] is provided to `commit`,
     ///   then [`Asg::add_edge`] will fail with that error.
-    fn pre_add_edge<
-        OA: ObjectIndexRelTo<OB>,
-        OB: ObjectKind + ObjectRelatable,
-    >(
+    ///
+    /// Unlike the type of [`Asg::add_edge`],
+    ///   the source [`ObjectIndex`] has been narrowed to the appropriate
+    ///   type for you.
+    fn pre_add_edge<OB: ObjectKind + ObjectRelatable>(
         asg: &mut Asg,
-        _from_oi: &OA,
+        _from_oi: ObjectIndex<Self>,
         _to_oi: ObjectIndex<OB>,
         _ctx_span: Option<Span>,
         commit: impl FnOnce(&mut Asg),
diff --git a/tamer/src/asg/graph/object/rel.rs b/tamer/src/asg/graph/object/rel.rs
index fa0855e0..3404cfd9 100644
--- a/tamer/src/asg/graph/object/rel.rs
+++ b/tamer/src/asg/graph/object/rel.rs
@@ -938,7 +938,13 @@ where
         ctx_span: Option<Span>,
         commit: impl FnOnce(&mut Asg),
     ) -> Result<(), AsgError> {
-        O::pre_add_edge(asg, self, to_oi, ctx_span, commit)
+        O::pre_add_edge(
+            asg,
+            self.widen().must_narrow_into::<O>(),
+            to_oi,
+            ctx_span,
+            commit,
+        )
     }
 }
 
@@ -962,7 +968,13 @@ impl<OB: ObjectRelatable> ObjectIndexRelTo<OB> for ObjectIndexTo<OB> {
     ) -> Result<(), AsgError> {
         macro_rules! pre_add_edge {
             ($ty:ident) => {
-                $ty::pre_add_edge(asg, self, to_oi, ctx_span, commit)
+                $ty::pre_add_edge(
+                    asg,
+                    self.widen().must_narrow_into::<$ty>(),
+                    to_oi,
+                    ctx_span,
+                    commit,
+                )
             };
         }