diff --git a/src/cmd/compile/internal/types2/named.go b/src/cmd/compile/internal/types2/named.go
index 8dd9fb6bc4..7b19aeb21f 100644
--- a/src/cmd/compile/internal/types2/named.go
+++ b/src/cmd/compile/internal/types2/named.go
@@ -78,6 +78,7 @@ func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, tpar
 }
 
 func (t *Named) cleanup() {
+	assert(t.orig.orig == t.orig)
 	// Ensure that every defined type created in the course of type-checking has
 	// either non-*Named underlying, or is unresolved.
 	//
diff --git a/src/go/types/named.go b/src/go/types/named.go
index b8760efc5e..4f855ece82 100644
--- a/src/go/types/named.go
+++ b/src/go/types/named.go
@@ -78,6 +78,7 @@ func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, tpar
 }
 
 func (t *Named) cleanup() {
+	assert(t.orig.orig == t.orig)
 	// Ensure that every defined type created in the course of type-checking has
 	// either non-*Named underlying, or is unresolved.
 	//