diff --git a/Userland/Libraries/LibIPC/Encoder.h b/Userland/Libraries/LibIPC/Encoder.h
index 3b5341b78a..508d5db348 100644
--- a/Userland/Libraries/LibIPC/Encoder.h
+++ b/Userland/Libraries/LibIPC/Encoder.h
@@ -37,20 +37,20 @@ public:
 
     ErrorOr<void> extend_capacity(size_t capacity)
     {
-        return m_buffer.data.try_ensure_capacity(m_buffer.data.size() + capacity);
+        TRY(m_buffer.extend_data_capacity(capacity));
+        return {};
     }
 
     ErrorOr<void> append(u8 const* values, size_t count)
     {
-        TRY(extend_capacity(count));
-        m_buffer.data.unchecked_append(values, count);
+        TRY(m_buffer.append_data(values, count));
         return {};
     }
 
     ErrorOr<void> append_file_descriptor(int fd)
     {
-        auto auto_fd = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) AutoCloseFileDescriptor(fd)));
-        return m_buffer.fds.try_append(move(auto_fd));
+        TRY(m_buffer.append_file_descriptor(fd));
+        return {};
     }
 
     ErrorOr<void> encode_size(size_t size);
diff --git a/Userland/Libraries/LibIPC/Forward.h b/Userland/Libraries/LibIPC/Forward.h
index 6be4a6197d..f1631faa93 100644
--- a/Userland/Libraries/LibIPC/Forward.h
+++ b/Userland/Libraries/LibIPC/Forward.h
@@ -13,7 +13,7 @@ namespace IPC {
 class Decoder;
 class Encoder;
 class Message;
-struct MessageBuffer;
+class MessageBuffer;
 class File;
 class Stub;
 
diff --git a/Userland/Libraries/LibIPC/Message.cpp b/Userland/Libraries/LibIPC/Message.cpp
index a6fe8c7212..ef96322b71 100644
--- a/Userland/Libraries/LibIPC/Message.cpp
+++ b/Userland/Libraries/LibIPC/Message.cpp
@@ -13,20 +13,45 @@ namespace IPC {
 
 using MessageSizeType = u32;
 
+MessageBuffer::MessageBuffer()
+{
+    m_data.resize(sizeof(MessageSizeType));
+}
+
+ErrorOr<void> MessageBuffer::extend_data_capacity(size_t capacity)
+{
+    TRY(m_data.try_ensure_capacity(m_data.size() + capacity));
+    return {};
+}
+
+ErrorOr<void> MessageBuffer::append_data(u8 const* values, size_t count)
+{
+    TRY(m_data.try_append(values, count));
+    return {};
+}
+
+ErrorOr<void> MessageBuffer::append_file_descriptor(int fd)
+{
+    auto auto_fd = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) AutoCloseFileDescriptor(fd)));
+    TRY(m_fds.try_append(move(auto_fd)));
+    return {};
+}
+
 ErrorOr<void> MessageBuffer::transfer_message(Core::LocalSocket& fd_passing_socket, Core::LocalSocket& data_socket)
 {
-    Checked<MessageSizeType> checked_message_size { data.size() };
+    Checked<MessageSizeType> checked_message_size { m_data.size() };
+    checked_message_size -= sizeof(MessageSizeType);
 
     if (checked_message_size.has_overflow())
         return Error::from_string_literal("Message is too large for IPC encoding");
 
     auto message_size = checked_message_size.value();
-    TRY(data.try_prepend(reinterpret_cast<u8 const*>(&message_size), sizeof(message_size)));
+    m_data.span().overwrite(0, reinterpret_cast<u8 const*>(&message_size), sizeof(message_size));
 
-    for (auto const& fd : fds)
+    for (auto const& fd : m_fds)
         TRY(fd_passing_socket.send_fd(fd->value()));
 
-    ReadonlyBytes bytes_to_write { data.span() };
+    ReadonlyBytes bytes_to_write { m_data.span() };
     size_t writes_done = 0;
 
     while (!bytes_to_write.is_empty()) {
@@ -59,7 +84,7 @@ ErrorOr<void> MessageBuffer::transfer_message(Core::LocalSocket& fd_passing_sock
     }
 
     if (writes_done > 1) {
-        dbgln("LibIPC::transfer_message FIXME Warning, needed {} writes needed to send message of size {}B, this is pretty bad, as it spins on the EventLoop", writes_done, data.size());
+        dbgln("LibIPC::transfer_message FIXME Warning, needed {} writes needed to send message of size {}B, this is pretty bad, as it spins on the EventLoop", writes_done, m_data.size());
     }
 
     return {};
diff --git a/Userland/Libraries/LibIPC/Message.h b/Userland/Libraries/LibIPC/Message.h
index eea9471e27..cf07a3b109 100644
--- a/Userland/Libraries/LibIPC/Message.h
+++ b/Userland/Libraries/LibIPC/Message.h
@@ -35,11 +35,20 @@ private:
     int m_fd;
 };
 
-struct MessageBuffer {
+class MessageBuffer {
+public:
+    MessageBuffer();
+
+    ErrorOr<void> extend_data_capacity(size_t capacity);
+    ErrorOr<void> append_data(u8 const* values, size_t count);
+
+    ErrorOr<void> append_file_descriptor(int fd);
+
     ErrorOr<void> transfer_message(Core::LocalSocket& fd_passing_socket, Core::LocalSocket& data_socket);
 
-    Vector<u8, 1024> data;
-    Vector<NonnullRefPtr<AutoCloseFileDescriptor>, 1> fds;
+private:
+    Vector<u8, 1024> m_data;
+    Vector<NonnullRefPtr<AutoCloseFileDescriptor>, 1> m_fds;
 };
 
 enum class ErrorCode : u32 {