diff --git a/buffet/any_internal_impl.h b/buffet/any_internal_impl.h
index 5d93200..d875e3b 100644
--- a/buffet/any_internal_impl.h
+++ b/buffet/any_internal_impl.h
@@ -40,7 +40,7 @@
   return false;
 }
 
-struct Buffer;  // Forward declaration of data buffer container.
+class Buffer;  // Forward declaration of data buffer container.
 
 // Abstract base class for contained variant data.
 struct Data {
diff --git a/buffet/any_internal_impl_unittest.cc b/buffet/any_internal_impl_unittest.cc
index fbc56fc..8c2fa58 100644
--- a/buffet/any_internal_impl_unittest.cc
+++ b/buffet/any_internal_impl_unittest.cc
@@ -39,7 +39,7 @@
   buffer.Assign(nullptr);
   EXPECT_FALSE(buffer.IsEmpty());
   EXPECT_EQ(Buffer::kContained, buffer.storage_);
-  EXPECT_EQ(typeid(nullptr_t), buffer.GetDataPtr()->GetType());
+  EXPECT_EQ(typeid(std::nullptr_t), buffer.GetDataPtr()->GetType());
 
   // char *
   buffer.Assign("abcd");