diff --git a/http2/adapter/http2_protocol.cc b/http2/adapter/http2_protocol.cc
index 8d59aee..dc0a57a 100644
--- a/http2/adapter/http2_protocol.cc
+++ b/http2/adapter/http2_protocol.cc
@@ -12,6 +12,10 @@
 const char kHttp2PathPseudoHeader[] = ":path";
 const char kHttp2StatusPseudoHeader[] = ":status";
 
+const uint8_t kMetadataFrameType = 0x4d;
+const uint8_t kMetadataEndFlag = 0x04;
+const uint16_t kMetadataExtensionId = 0x4d44;
+
 std::pair<absl::string_view, bool> GetStringView(const HeaderRep& rep) {
   if (absl::holds_alternative<absl::string_view>(rep)) {
     return std::make_pair(absl::get<absl::string_view>(rep), true);
diff --git a/http2/adapter/http2_protocol.h b/http2/adapter/http2_protocol.h
index 5e892e0..9f72fbe 100644
--- a/http2/adapter/http2_protocol.h
+++ b/http2/adapter/http2_protocol.h
@@ -67,6 +67,11 @@
 ABSL_CONST_INIT QUICHE_EXPORT_PRIVATE extern const char
     kHttp2StatusPseudoHeader[];
 
+ABSL_CONST_INIT QUICHE_EXPORT_PRIVATE extern const uint8_t kMetadataFrameType;
+ABSL_CONST_INIT QUICHE_EXPORT_PRIVATE extern const uint8_t kMetadataEndFlag;
+ABSL_CONST_INIT QUICHE_EXPORT_PRIVATE extern const uint16_t
+    kMetadataExtensionId;
+
 enum class FrameType : uint8_t {
   DATA = 0x0,
   HEADERS,
@@ -131,10 +136,6 @@
   kServer,
 };
 
-inline constexpr uint8_t kMetadataFrameType = 0x4d;
-inline constexpr uint8_t kMetadataEndFlag = 0x04;
-inline constexpr uint16_t kMetadataExtensionId = 0x4d44;
-
 }  // namespace adapter
 }  // namespace http2