diff --git a/src/go/ast/scope.go b/src/go/ast/scope.go
index df1529d1819..1ce5e2e84b5 100644
--- a/src/go/ast/scope.go
+++ b/src/go/ast/scope.go
@@ -38,7 +38,7 @@ func (s *Scope) Lookup(name string) *Object {
 // Insert attempts to insert a named object obj into the scope s.
 // If the scope already contains an object alt with the same name,
 // Insert leaves the scope unchanged and returns alt. Otherwise
-// it inserts obj and returns nil."
+// it inserts obj and returns nil.
 //
 func (s *Scope) Insert(obj *Object) (alt *Object) {
 	if alt = s.Objects[obj.Name]; alt == nil {