diff --git a/src/input/AsyncInputStream.cxx b/src/input/AsyncInputStream.cxx
index 8aefac0eb..9133dada4 100644
--- a/src/input/AsyncInputStream.cxx
+++ b/src/input/AsyncInputStream.cxx
@@ -217,23 +217,28 @@ AsyncInputStream::CommitWriteBuffer(size_t nbytes) noexcept
 }
 
 void
-AsyncInputStream::AppendToBuffer(const void *data, size_t append_size) noexcept
+AsyncInputStream::AppendToBuffer(std::span<const std::byte> src) noexcept
 {
 	auto w = buffer.Write();
 	assert(!w.empty());
 
-	size_t nbytes = std::min(w.size(), append_size);
-	memcpy(w.data(), data, nbytes);
-	buffer.Append(nbytes);
+	std::span<const std::byte> second{};
 
-	const size_t remaining = append_size - nbytes;
-	if (remaining > 0) {
+	if (w.size() < src.size()) {
+		second = src.subspan(w.size());
+		src = src.first(w.size());
+	}
+
+	std::copy(src.begin(), src.end(), w.begin());
+	buffer.Append(src.size());
+
+	if (!second.empty()) {
 		w = buffer.Write();
 		assert(!w.empty());
-		assert(w.size() >= remaining);
+		assert(w.size() >= second.size());
 
-		memcpy(w.data(), (const std::byte *)data + nbytes, remaining);
-		buffer.Append(remaining);
+		std::copy(second.begin(), second.end(), w.begin());
+		buffer.Append(second.size());
 	}
 
 	if (!IsReady())
diff --git a/src/input/AsyncInputStream.hxx b/src/input/AsyncInputStream.hxx
index a7160af8a..80e6c40a5 100644
--- a/src/input/AsyncInputStream.hxx
+++ b/src/input/AsyncInputStream.hxx
@@ -139,7 +139,7 @@ protected:
 	 * Append data to the buffer.  The size must fit into the
 	 * buffer; see GetBufferSpace().
 	 */
-	void AppendToBuffer(const void *data, size_t append_size) noexcept;
+	void AppendToBuffer(std::span<const std::byte> src) noexcept;
 
 	/**
 	 * Implement code here that will resume the stream after it
diff --git a/src/input/plugins/CurlInputPlugin.cxx b/src/input/plugins/CurlInputPlugin.cxx
index db1da42d5..fe6e4ae7c 100644
--- a/src/input/plugins/CurlInputPlugin.cxx
+++ b/src/input/plugins/CurlInputPlugin.cxx
@@ -353,7 +353,7 @@ CurlInputStream::OnData(std::span<const std::byte> data)
 		throw CurlResponseHandler::Pause{};
 	}
 
-	AppendToBuffer(data.data(), data.size());
+	AppendToBuffer(data);
 }
 
 void
diff --git a/src/input/plugins/NfsInputPlugin.cxx b/src/input/plugins/NfsInputPlugin.cxx
index 12da41ab0..b64cf7388 100644
--- a/src/input/plugins/NfsInputPlugin.cxx
+++ b/src/input/plugins/NfsInputPlugin.cxx
@@ -164,7 +164,8 @@ NfsInputStream::OnNfsFileRead(std::span<const std::byte> src) noexcept
 	const std::scoped_lock<Mutex> protect(mutex);
 	assert(!IsBufferFull());
 	assert(IsBufferFull() == (GetBufferSpace() == 0));
-	AppendToBuffer(src.data(), src.size());
+
+	AppendToBuffer(src);
 
 	next_offset += src.size();