diff --git a/src/hotspot/share/gc/serial/defNewGeneration.hpp b/src/hotspot/share/gc/serial/defNewGeneration.hpp
index 5c8dd08e40b..a7ee555902a 100644
--- a/src/hotspot/share/gc/serial/defNewGeneration.hpp
+++ b/src/hotspot/share/gc/serial/defNewGeneration.hpp
@@ -43,7 +43,6 @@ class CSpaceCounters;
 class OldGenScanClosure;
 class YoungGenScanClosure;
 class DefNewTracer;
-class ScanWeakRefClosure;
 class SerialHeap;
 class STWGCTimer;
 
diff --git a/src/hotspot/share/gc/serial/serialHeap.hpp b/src/hotspot/share/gc/serial/serialHeap.hpp
index 14e0d737c1a..750bb322b2a 100644
--- a/src/hotspot/share/gc/serial/serialHeap.hpp
+++ b/src/hotspot/share/gc/serial/serialHeap.hpp
@@ -72,14 +72,8 @@ class SerialHeap : public CollectedHeap {
   friend class HeapInspection;
   friend class GCCauseSetter;
   friend class VMStructs;
-public:
   friend class VM_PopulateDumpSharedSpace;
 
-  enum GenerationType {
-    YoungGen,
-    OldGen
-  };
-
 private:
   DefNewGeneration* _young_gen;
   TenuredGeneration* _old_gen;
@@ -124,7 +118,6 @@ public:
   // Does operations required after initialization has been done.
   void post_initialize() override;
 
-  bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
   bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
 
   // Performance Counter support