diff --git a/CMakeLists.txt b/CMakeLists.txt
index c92ebee..1ae8d00 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -49,6 +49,7 @@ set(LIBDATACHANNEL_SOURCES
 	${CMAKE_CURRENT_SOURCE_DIR}/src/icetransport.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/init.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/log.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/message.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/peerconnection.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/rtc.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/sctptransport.cpp
diff --git a/include/rtc/message.hpp b/include/rtc/message.hpp
index 1928521..e79fb0b 100644
--- a/include/rtc/message.hpp
+++ b/include/rtc/message.hpp
@@ -1,5 +1,5 @@
 /**
- * Copyright (c) 2019 Paul-Louis Ageneau
+ * Copyright (c) 2019-2020 Paul-Louis Ageneau
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -50,7 +50,7 @@ using message_ptr = std::shared_ptr<Message>;
 using message_callback = std::function<void(message_ptr message)>;
 using message_variant = std::variant<binary, string>;
 
-constexpr auto message_size_func = [](const message_ptr &m) -> size_t {
+inline size_t message_size_func(const message_ptr &m) {
 	return m->type == Message::Binary || m->type == Message::String ? m->size() : 0;
 };
 
@@ -64,47 +64,16 @@ message_ptr make_message(Iterator begin, Iterator end, Message::Type type = Mess
 	return message;
 }
 
-inline message_ptr make_message(size_t size, Message::Type type = Message::Binary,
-                                unsigned int stream = 0,
-                                std::shared_ptr<Reliability> reliability = nullptr) {
-	auto message = std::make_shared<Message>(size, type);
-	message->stream = stream;
-	message->reliability = reliability;
-	return message;
-}
+message_ptr make_message(size_t size, Message::Type type = Message::Binary, unsigned int stream = 0,
+                         std::shared_ptr<Reliability> reliability = nullptr);
 
-inline message_ptr make_message(binary &&data, Message::Type type = Message::Binary,
-                                unsigned int stream = 0,
-                                std::shared_ptr<Reliability> reliability = nullptr) {
-	auto message = std::make_shared<Message>(std::move(data), type);
-	message->stream = stream;
-	message->reliability = reliability;
-	return message;
-}
+message_ptr make_message(binary &&data, Message::Type type = Message::Binary,
+                         unsigned int stream = 0,
+                         std::shared_ptr<Reliability> reliability = nullptr);
 
-inline message_ptr make_message(message_variant data) {
-	return std::visit( //
-	    overloaded{
-	        [&](binary data) { return make_message(std::move(data), Message::Binary); },
-	        [&](string data) {
-		        auto b = reinterpret_cast<const byte *>(data.data());
-		        return make_message(b, b + data.size(), Message::String);
-	        },
-	    },
-	    std::move(data));
-}
+message_ptr make_message(message_variant data);
 
-inline std::optional<message_variant> to_variant(Message &&message) {
-	switch (message.type) {
-	case Message::String:
-		return std::make_optional(
-		    string(reinterpret_cast<const char *>(message.data()), message.size()));
-	case Message::Binary:
-		return std::make_optional(std::move(message));
-	default:
-		return nullopt;
-	}
-}
+std::optional<message_variant> to_variant(Message &&message);
 
 } // namespace rtc
 
diff --git a/src/message.cpp b/src/message.cpp
new file mode 100644
index 0000000..0dccc61
--- /dev/null
+++ b/src/message.cpp
@@ -0,0 +1,63 @@
+/**
+ * Copyright (c) 2019-2020 Paul-Louis Ageneau
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "message.hpp"
+
+namespace rtc {
+
+message_ptr make_message(size_t size, Message::Type type, unsigned int stream,
+                         std::shared_ptr<Reliability> reliability) {
+	auto message = std::make_shared<Message>(size, type);
+	message->stream = stream;
+	message->reliability = reliability;
+	return message;
+}
+
+message_ptr make_message(binary &&data, Message::Type type, unsigned int stream,
+                         std::shared_ptr<Reliability> reliability) {
+	auto message = std::make_shared<Message>(std::move(data), type);
+	message->stream = stream;
+	message->reliability = reliability;
+	return message;
+}
+
+message_ptr make_message(message_variant data) {
+	return std::visit( //
+	    overloaded{
+	        [&](binary data) { return make_message(std::move(data), Message::Binary); },
+	        [&](string data) {
+		        auto b = reinterpret_cast<const byte *>(data.data());
+		        return make_message(b, b + data.size(), Message::String);
+	        },
+	    },
+	    std::move(data));
+}
+
+std::optional<message_variant> to_variant(Message &&message) {
+	switch (message.type) {
+	case Message::String:
+		return std::make_optional(
+		    string(reinterpret_cast<const char *>(message.data()), message.size()));
+	case Message::Binary:
+		return std::make_optional(std::move(message));
+	default:
+		return nullopt;
+	}
+}
+
+} // namespace rtc