diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index daec096..7f463a3 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -5451,6 +5451,8 @@
   kArrayCheck             // No optimization yet when checking against a generic array.
 };
 
+std::ostream& operator<<(std::ostream& os, TypeCheckKind rhs);
+
 class HInstanceOf : public HExpression<2> {
  public:
   HInstanceOf(HInstruction* object,