diff --git a/aos/ipc_lib/lockless_queue.cc b/aos/ipc_lib/lockless_queue.cc
index 0c87e4d..3fb506b 100644
--- a/aos/ipc_lib/lockless_queue.cc
+++ b/aos/ipc_lib/lockless_queue.cc
@@ -239,6 +239,12 @@
 
 }  // namespace
 
+size_t LocklessQueueConfiguration::message_size() const {
+  // Round up the message size so following data is aligned appropriately.
+  return LocklessQueueMemory::AlignmentRoundUp(message_data_size) +
+         sizeof(Message);
+}
+
 size_t LocklessQueueMemorySize(LocklessQueueConfiguration config) {
   // Round up the message size so following data is aligned appropriately.
   config.message_data_size =
@@ -278,8 +284,7 @@
     memory->config.num_watchers = config.num_watchers;
     memory->config.num_senders = config.num_senders;
     memory->config.queue_size = config.queue_size;
-    memory->config.message_data_size =
-        LocklessQueueMemory::AlignmentRoundUp(config.message_data_size);
+    memory->config.message_data_size = config.message_data_size;
 
     const size_t num_messages = memory->num_messages();
     // There need to be at most MaxMessages() messages allocated.
diff --git a/aos/ipc_lib/lockless_queue.h b/aos/ipc_lib/lockless_queue.h
index 4a8523b..d539386 100644
--- a/aos/ipc_lib/lockless_queue.h
+++ b/aos/ipc_lib/lockless_queue.h
@@ -83,7 +83,7 @@
   // Size in bytes of the data stored in each Message.
   size_t message_data_size;
 
-  size_t message_size() const { return message_data_size + sizeof(Message); }
+  size_t message_size() const;
 
   size_t num_messages() const { return num_senders + queue_size; }
 };