diff --git a/src/compiler/simplified-operator-reducer.h b/src/compiler/simplified-operator-reducer.h
index 979a3d0..13301c2 100644
--- a/src/compiler/simplified-operator-reducer.h
+++ b/src/compiler/simplified-operator-reducer.h
@@ -9,6 +9,10 @@
 
 namespace v8 {
 namespace internal {
+
+// Forward declarations.
+class TypeCache;
+
 namespace compiler {
 
 // Forward declarations.
@@ -42,6 +46,7 @@
   SimplifiedOperatorBuilder* simplified() const;
 
   JSGraph* const jsgraph_;
+  TypeCache const& type_cache_;
 
   DISALLOW_COPY_AND_ASSIGN(SimplifiedOperatorReducer);
 };