diff --git a/runtime/sam/expr/function/downcast.go b/runtime/sam/expr/function/downcast.go
index da9a99f9f..04697cd6c 100644
--- a/runtime/sam/expr/function/downcast.go
+++ b/runtime/sam/expr/function/downcast.go
@@ -44,6 +44,7 @@ func (d *downcast) downcast(b *scode.Builder, typ super.Type, bytes scode.Bytes,
 		superBytes, _ := superType.Deref(d.sctx, bytes)
 		return d.downcast(b, superType.Type, superBytes, to)
 	}
+	typ = super.TypeUnder(typ)
 	switch to := to.(type) {
 	case *super.TypeRecord:
 		return d.toRecord(b, typ, bytes, to)
@@ -58,7 +59,7 @@ func (d *downcast) downcast(b *scode.Builder, typ super.Type, bytes scode.Bytes,
 	case *super.TypeError:
 		return d.toError(b, typ, bytes, to)
 	case *super.TypeNamed:
-		return d.toNamed(b, typ, bytes, to)
+		return d.downcast(b, typ, bytes, to.Type)
 	case *super.TypeFusion:
 		// Can't downcast to a super type
 		return false
@@ -171,13 +172,6 @@ func (d *downcast) toError(b *scode.Builder, typ super.Type, bytes scode.Bytes,
 	return false
 }
 
-func (d *downcast) toNamed(b *scode.Builder, typ super.Type, bytes scode.Bytes, to *super.TypeNamed) bool {
-	if namedType, ok := typ.(*super.TypeNamed); ok {
-		return d.downcast(b, namedType.Type, bytes, to.Type)
-	}
-	return false
-}
-
 func (d *downcast) subTypeOf(typ super.Type, bytes scode.Bytes, types []super.Type) int {
 	// XXX TBD we should make a subtype() function that returns true if a type is
 	// a subtype of another and use that here and expose it to the language.
diff --git a/runtime/ztests/expr/function/defuse.yaml b/runtime/ztests/expr/function/defuse.yaml
index 286b59189..2822eee1e 100644
--- a/runtime/ztests/expr/function/defuse.yaml
+++ b/runtime/ztests/expr/function/defuse.yaml
@@ -19,3 +19,18 @@ input: &input |
 
 output: *input
 
+---
+
+spq: fuse | defuse(this)
+
+input: &input |
+  1::=p1
+  {a:{b:1::=r1}::=r2}::=r3
+  [[1::=a1]::=a2]::=a3
+  |[|[1::=s1]|::=s2]|::=s3
+  |{1::=m1:2::=m2}|::=m3
+  "a"::(en1=enum(a,b))
+  1::=n1::(n2=n1|(n3=string))
+  error(1::=er1)::=er2
+
+output: *input