diff --git a/src/event/FullyBufferedSocket.cxx b/src/event/FullyBufferedSocket.cxx
index ca9db4dc0..b20457627 100644
--- a/src/event/FullyBufferedSocket.cxx
+++ b/src/event/FullyBufferedSocket.cxx
@@ -8,10 +8,10 @@
 
 #include <string.h>
 
-FullyBufferedSocket::ssize_t
-FullyBufferedSocket::DirectWrite(const void *data, size_t length) noexcept
+inline FullyBufferedSocket::ssize_t
+FullyBufferedSocket::DirectWrite(std::span<const std::byte> src) noexcept
 {
-	const auto nbytes = GetSocket().Write((const char *)data, length);
+	const auto nbytes = GetSocket().Write((const char *)src.data(), src.size());
 	if (nbytes < 0) [[unlikely]] {
 		const auto code = GetSocketError();
 		if (IsSocketErrorSendWouldBlock(code))
@@ -41,7 +41,7 @@ FullyBufferedSocket::Flush() noexcept
 		return true;
 	}
 
-	auto nbytes = DirectWrite(data.data(), data.size());
+	auto nbytes = DirectWrite(data);
 	if (nbytes <= 0) [[unlikely]]
 		return nbytes == 0;
 
diff --git a/src/event/FullyBufferedSocket.hxx b/src/event/FullyBufferedSocket.hxx
index 586f37645..0955d3abc 100644
--- a/src/event/FullyBufferedSocket.hxx
+++ b/src/event/FullyBufferedSocket.hxx
@@ -1,13 +1,14 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 // Copyright The Music Player Daemon Project
 
-#ifndef MPD_FULLY_BUFFERED_SOCKET_HXX
-#define MPD_FULLY_BUFFERED_SOCKET_HXX
+#pragma once
 
 #include "BufferedSocket.hxx"
 #include "IdleEvent.hxx"
 #include "util/PeakBuffer.hxx"
 
+#include <span>
+
 /**
  * A #BufferedSocket specialization that adds an output buffer.
  */
@@ -42,7 +43,7 @@ private:
 	 * socket isn't ready for writing, -1 on error (the socket has
 	 * been closed and probably destructed)
 	 */
-	ssize_t DirectWrite(const void *data, size_t length) noexcept;
+	ssize_t DirectWrite(std::span<const std::byte> src) noexcept;
 
 protected:
 	/**
@@ -62,5 +63,3 @@ protected:
 	/* virtual methods from class BufferedSocket */
 	void OnSocketReady(unsigned flags) noexcept override;
 };
-
-#endif