diff --git a/compiler/optimizing/graph_checker.h b/compiler/optimizing/graph_checker.h
index ae1557b..5ec3003 100644
--- a/compiler/optimizing/graph_checker.h
+++ b/compiler/optimizing/graph_checker.h
@@ -60,6 +60,11 @@
   }
 
  protected:
+  // Report a new error.
+  void AddError(const std::string& error) {
+    errors_.push_back(error);
+  }
+
   ArenaAllocator* const allocator_;
   // The block currently visited.
   HBasicBlock* current_block_ = nullptr;