diff --git a/thrift/lib/thrift/TypeToMaskAdapter.cpp b/thrift/lib/thrift/TypeToMaskAdapter.cpp
index 9f60456e2b4..2945a595181 100644
--- a/thrift/lib/thrift/TypeToMaskAdapter.cpp
+++ b/thrift/lib/thrift/TypeToMaskAdapter.cpp
@@ -18,10 +18,10 @@
 
 #include <thrift/lib/cpp2/protocol/DebugProtocol.h>
 
-namespace apache::thrift::detail {
+namespace apache::thrift::protocol::detail {
 
 std::string debugFormatType(const type::Type& type) {
   return debugStringViaEncode(type);
 }
 
-} // namespace apache::thrift::detail
+} // namespace apache::thrift::protocol::detail
diff --git a/thrift/lib/thrift/TypeToMaskAdapter.h b/thrift/lib/thrift/TypeToMaskAdapter.h
index fcdb22521ee..5ba45f221f3 100644
--- a/thrift/lib/thrift/TypeToMaskAdapter.h
+++ b/thrift/lib/thrift/TypeToMaskAdapter.h
@@ -20,7 +20,7 @@
 #include <folly/container/F14Map.h>
 #include <thrift/lib/thrift/gen-cpp2/type_types.h>
 
-namespace apache::thrift::detail {
+namespace apache::thrift::protocol::detail {
 
 std::string debugFormatType(const type::Type& type);
 
@@ -75,4 +75,4 @@ class TypeToMaskAdapter {
   // materializing intermediate thrift struct)
 };
 
-} // namespace apache::thrift::detail
+} // namespace apache::thrift::protocol::detail
diff --git a/thrift/lib/thrift/field_mask.thrift b/thrift/lib/thrift/field_mask.thrift
index d10205c63c0..461ab4c105d 100644
--- a/thrift/lib/thrift/field_mask.thrift
+++ b/thrift/lib/thrift/field_mask.thrift
@@ -52,7 +52,7 @@ struct TypeAndMaskEntry {
  * given type within the list
  */
 @cpp.Adapter{
-  name = "::apache::thrift::detail::TypeToMaskAdapter<
+  name = "::apache::thrift::protocol::detail::TypeToMaskAdapter<
       ::apache::thrift::protocol::TypeAndMaskEntry,
       ::apache::thrift::protocol::Mask
     >",
diff --git a/thrift/test/FieldMaskTest.cpp b/thrift/test/FieldMaskTest.cpp
index 7d0077ab1b4..eecfb149d0a 100644
--- a/thrift/test/FieldMaskTest.cpp
+++ b/thrift/test/FieldMaskTest.cpp
@@ -3532,9 +3532,8 @@ TEST(FieldMaskTest, testDuplicateEntryInTypeMaskList) {
   entries.emplace_back().type() = type::infer_tag<Foo>{};
 
   EXPECT_THROW(
-      (::apache::thrift::detail::
-           TypeToMaskAdapter<protocol::TypeAndMaskEntry, Mask>::fromThrift(
-               std::move(entries))),
+      (protocol::detail::TypeToMaskAdapter<protocol::TypeAndMaskEntry, Mask>::
+           fromThrift(std::move(entries))),
       std::runtime_error);
 }