diff --git a/src/google/protobuf/reflection.h b/src/google/protobuf/reflection.h
index b493fcc738ac..9b5208c55448 100644
--- a/src/google/protobuf/reflection.h
+++ b/src/google/protobuf/reflection.h
@@ -13,6 +13,7 @@
 #include <memory>
 #include <type_traits>
 
+#include "absl/base/attributes.h"
 #include "google/protobuf/generated_enum_util.h"
 #include "google/protobuf/descriptor.h"
 
@@ -96,6 +97,8 @@ class MutableRepeatedFieldRef<
   }
   void Add(const T& value) const { accessor_->template Add<T>(data_, value); }
   void RemoveLast() const { accessor_->RemoveLast(data_); }
+  // TODO: Remove.
+  ABSL_DEPRECATED("Do not use. Will be removed in a future release.")
   void Reserve(int size) const { accessor_->Reserve(data_, size); }
   void SwapElements(int index1, int index2) const {
     accessor_->SwapElements(data_, index1, index2);
@@ -215,6 +218,8 @@ class MutableRepeatedFieldRef<
   }
   void Add(const T& value) const { accessor_->Add(data_, &value); }
   void RemoveLast() const { accessor_->RemoveLast(data_); }
+  // TODO: Remove.
+  ABSL_DEPRECATED("Do not use. Will be removed in a future release.")
   void Reserve(int size) const { accessor_->Reserve(data_, size); }
   void SwapElements(int index1, int index2) const {
     accessor_->SwapElements(data_, index1, index2);
@@ -303,6 +308,8 @@ class PROTOBUF_EXPORT RepeatedFieldAccessor {
   virtual void Set(Field* data, int index, const Value* value) const = 0;
   virtual void Add(Field* data, const Value* value) const = 0;
   virtual void RemoveLast(Field* data) const = 0;
+  // TODO: Remove.
+  ABSL_DEPRECATED("Do not use. Will be removed in a future release.")
   virtual void Reserve(Field* data, int size) const = 0;
   virtual void SwapElements(Field* data, int index1, int index2) const = 0;
   virtual void Swap(Field* data, const RepeatedFieldAccessor* other_mutator,
diff --git a/src/google/protobuf/reflection_internal.h b/src/google/protobuf/reflection_internal.h
index ea4bac293a18..6d8008801977 100644
--- a/src/google/protobuf/reflection_internal.h
+++ b/src/google/protobuf/reflection_internal.h
@@ -87,6 +87,7 @@ class RepeatedFieldWrapper : public RandomAccessRepeatedFieldAccessor {
   void RemoveLast(Field* data) const override {
     MutableRepeatedField(data)->RemoveLast();
   }
+  // TODO: Remove.
   void Reserve(Field* data, int size) const override {
     MutableRepeatedField(data)->Reserve(size);
   }
@@ -146,6 +147,7 @@ class RepeatedPtrFieldWrapper : public RandomAccessRepeatedFieldAccessor {
   void RemoveLast(Field* data) const override {
     MutableRepeatedField(data)->RemoveLast();
   }
+  // TODO: Remove.
   void Reserve(Field* data, int size) const override {
     MutableRepeatedField(data)->Reserve(size);
   }