diff --git a/src/clang_symbol_kind.h b/src/clang_symbol_kind.h
index eb3df27a..c168ae79 100644
--- a/src/clang_symbol_kind.h
+++ b/src/clang_symbol_kind.h
@@ -41,8 +41,7 @@ enum class ClangSymbolKind : uint8_t {
   Parameter = 25,
   Using,
 };
-MAKE_REFLECT_TYPE_PROXY(ClangSymbolKind,
-                        std::underlying_type<ClangSymbolKind>::type);
+MAKE_REFLECT_TYPE_PROXY(ClangSymbolKind);
 
 // clang/Basic/Specifiers.h clang::StorageClass
 enum class StorageClass : uint8_t {
@@ -63,7 +62,7 @@ enum class StorageClass : uint8_t {
   Auto,
   Register
 };
-MAKE_REFLECT_TYPE_PROXY(StorageClass, std::underlying_type<StorageClass>::type);
+MAKE_REFLECT_TYPE_PROXY(StorageClass);
 
 enum class SymbolRole : uint8_t {
   Declaration = 1 << 0,
@@ -75,7 +74,7 @@ enum class SymbolRole : uint8_t {
   BaseOf = 1 << 5,
   CalledBy = 1 << 6,
 };
-MAKE_REFLECT_TYPE_PROXY(SymbolRole, std::underlying_type<SymbolRole>::type);
+MAKE_REFLECT_TYPE_PROXY(SymbolRole);
 
 inline uint8_t operator&(SymbolRole lhs, SymbolRole rhs) {
   return uint8_t(lhs) & uint8_t(rhs);
diff --git a/src/indexer.h b/src/indexer.h
index 7ded5c13..3b963201 100644
--- a/src/indexer.h
+++ b/src/indexer.h
@@ -34,7 +34,7 @@ using namespace std::experimental;
 // The order matters. In FindSymbolsAtLocation, we want Var/Func ordered in
 // front of others.
 enum class SymbolKind : uint8_t { Invalid, File, Type, Func, Var };
-MAKE_REFLECT_TYPE_PROXY(SymbolKind, uint8_t);
+MAKE_REFLECT_TYPE_PROXY(SymbolKind);
 
 template <typename T>
 struct Id {
@@ -480,7 +480,7 @@ struct IndexInclude {
 // a file previously identified as `C`, will be changed to `Cpp` if it
 // encounters a c++ declaration.
 enum class LanguageId { Unknown = 0, C = 1, Cpp = 2, ObjC = 3 };
-MAKE_REFLECT_TYPE_PROXY(LanguageId, std::underlying_type<LanguageId>::type);
+MAKE_REFLECT_TYPE_PROXY(LanguageId);
 
 struct IndexFile {
   IdCache id_cache;
diff --git a/src/ipc.h b/src/ipc.h
index 91e20957..aaab0055 100644
--- a/src/ipc.h
+++ b/src/ipc.h
@@ -67,7 +67,7 @@ enum class IpcId : int {
   CqueryWait,
 };
 MAKE_ENUM_HASHABLE(IpcId)
-MAKE_REFLECT_TYPE_PROXY(IpcId, int)
+MAKE_REFLECT_TYPE_PROXY(IpcId)
 const char* IpcIdToString(IpcId id);
 
 struct BaseIpcMessage {
diff --git a/src/language_server_api.h b/src/language_server_api.h
index a0b99f9f..6eb5046f 100644
--- a/src/language_server_api.h
+++ b/src/language_server_api.h
@@ -199,7 +199,7 @@ enum class lsSymbolKind : int {
   Boolean = 17,
   Array = 18
 };
-MAKE_REFLECT_TYPE_PROXY(lsSymbolKind, int);
+MAKE_REFLECT_TYPE_PROXY(lsSymbolKind);
 
 struct lsSymbolInformation {
   std::string name;
@@ -301,7 +301,7 @@ enum class lsInsertTextFormat {
   // https://github.com/Microsoft/vscode/blob/master/src/vs/editor/contrib/snippet/common/snippet.md
   Snippet = 2
 };
-MAKE_REFLECT_TYPE_PROXY(lsInsertTextFormat, int);
+MAKE_REFLECT_TYPE_PROXY(lsInsertTextFormat);
 
 // The kind of a completion entry.
 enum class lsCompletionItemKind {
@@ -331,7 +331,7 @@ enum class lsCompletionItemKind {
   Operator = 24,
   TypeParameter = 25,
 };
-MAKE_REFLECT_TYPE_PROXY(lsCompletionItemKind, int);
+MAKE_REFLECT_TYPE_PROXY(lsCompletionItemKind);
 
 struct lsCompletionItem {
   // A set of function parameters. Used internally for signature help. Not sent
@@ -455,7 +455,7 @@ enum class lsDocumentHighlightKind {
   // Write-access of a symbol, like writing to a variable.
   Write = 3
 };
-MAKE_REFLECT_TYPE_PROXY(lsDocumentHighlightKind, int);
+MAKE_REFLECT_TYPE_PROXY(lsDocumentHighlightKind);
 
 struct lsFormattingOptions {
   // Size of a tab in spaces.
@@ -487,7 +487,7 @@ enum class lsDiagnosticSeverity {
   // Reports a hint.
   Hint = 4
 };
-MAKE_REFLECT_TYPE_PROXY(lsDiagnosticSeverity, int);
+MAKE_REFLECT_TYPE_PROXY(lsDiagnosticSeverity);
 
 struct lsDiagnostic {
   // The range at which the message applies.
@@ -527,7 +527,7 @@ enum class lsErrorCodes {
   // Defined by the protocol.
   RequestCancelled = -32800,
 };
-MAKE_REFLECT_TYPE_PROXY(lsErrorCodes, int);
+MAKE_REFLECT_TYPE_PROXY(lsErrorCodes);
 struct Out_Error : public lsOutMessage<Out_Error> {
   struct lsResponseError {
     // A number indicating the error type that occurred.
@@ -621,7 +621,7 @@ MAKE_REFLECT_STRUCT(lsTextDocumentDidChangeParams,
 
 // Show a message to the user.
 enum class lsMessageType : int { Error = 1, Warning = 2, Info = 3, Log = 4 };
-MAKE_REFLECT_TYPE_PROXY(lsMessageType, int)
+MAKE_REFLECT_TYPE_PROXY(lsMessageType)
 struct Out_ShowLogMessageParams {
   lsMessageType type = lsMessageType::Error;
   std::string message;
diff --git a/src/messages/cquery_call_tree.cc b/src/messages/cquery_call_tree.cc
index 06b245c2..fb71005e 100644
--- a/src/messages/cquery_call_tree.cc
+++ b/src/messages/cquery_call_tree.cc
@@ -39,7 +39,7 @@ struct Out_CqueryCallTree : public lsOutMessage<Out_CqueryCallTree> {
   lsRequestId id;
   std::vector<CallEntry> result;
 };
-MAKE_REFLECT_TYPE_PROXY(Out_CqueryCallTree::CallType, int);
+MAKE_REFLECT_TYPE_PROXY(Out_CqueryCallTree::CallType);
 MAKE_REFLECT_STRUCT(Out_CqueryCallTree::CallEntry,
                     name,
                     usr,
diff --git a/src/messages/initialize.cc b/src/messages/initialize.cc
index 1be67519..6c2c57d3 100644
--- a/src/messages/initialize.cc
+++ b/src/messages/initialize.cc
@@ -98,7 +98,7 @@ enum class lsTextDocumentSyncKind {
   // send.
   Incremental = 2
 };
-MAKE_REFLECT_TYPE_PROXY(lsTextDocumentSyncKind, int)
+MAKE_REFLECT_TYPE_PROXY(lsTextDocumentSyncKind)
 
 struct lsTextDocumentSyncOptions {
   // Open and close notifications are sent to the server.
diff --git a/src/messages/text_document_completion.cc b/src/messages/text_document_completion.cc
index 681d4b54..1286e511 100644
--- a/src/messages/text_document_completion.cc
+++ b/src/messages/text_document_completion.cc
@@ -22,8 +22,7 @@ enum class lsCompletionTriggerKind {
   // the `triggerCharacters` properties of the `CompletionRegistrationOptions`.
   TriggerCharacter = 2
 };
-MAKE_REFLECT_TYPE_PROXY(lsCompletionTriggerKind,
-                        std::underlying_type<lsCompletionTriggerKind>::type);
+MAKE_REFLECT_TYPE_PROXY(lsCompletionTriggerKind);
 
 // Contains additional information about the context in which a completion
 // request is triggered.
diff --git a/src/messages/workspace_did_change_watched_files.cc b/src/messages/workspace_did_change_watched_files.cc
index 80003af4..671676e2 100644
--- a/src/messages/workspace_did_change_watched_files.cc
+++ b/src/messages/workspace_did_change_watched_files.cc
@@ -12,8 +12,7 @@ enum class lsFileChangeType {
   Changed = 2,
   Deleted = 3,
 };
-MAKE_REFLECT_TYPE_PROXY(lsFileChangeType,
-                        std::underlying_type<lsFileChangeType>::type);
+MAKE_REFLECT_TYPE_PROXY(lsFileChangeType);
 
 struct lsFileEvent {
   lsDocumentUri uri;
diff --git a/src/serializer.h b/src/serializer.h
index d81e4f18..92f9c8ee 100644
--- a/src/serializer.h
+++ b/src/serializer.h
@@ -78,8 +78,9 @@ struct IndexFile;
 #define REFLECT_MEMBER(name) ReflectMember(visitor, #name, value.name)
 #define REFLECT_MEMBER2(name, value) ReflectMember(visitor, name, value)
 
-// TODO Make it inline because this macro can be used in header files.
-#define MAKE_REFLECT_TYPE_PROXY(type, as_type)                         \
+#define MAKE_REFLECT_TYPE_PROXY(type_name) \
+  MAKE_REFLECT_TYPE_PROXY2(type_name, std::underlying_type<type_name>::type)
+#define MAKE_REFLECT_TYPE_PROXY2(type, as_type)                        \
   ATTRIBUTE_UNUSED inline void Reflect(Reader& visitor, type& value) { \
     as_type value0;                                                    \
     ::Reflect(visitor, value0);                                        \