diff --git a/dlls/ntdll/unix/file.c b/dlls/ntdll/unix/file.c
index 8313e3c3160..0db2bd4ffce 100644
--- a/dlls/ntdll/unix/file.c
+++ b/dlls/ntdll/unix/file.c
@@ -4610,15 +4610,6 @@ NTSTATUS WINAPI NtSetInformationFile( HANDLE handle, IO_STATUS_BLOCK *io,
  *                  Asynchronous file I/O                              *
  */
 
-typedef NTSTATUS async_callback_t( void *user, IO_STATUS_BLOCK *io, NTSTATUS status );
-
-struct async_fileio
-{
-    async_callback_t    *callback; /* must be the first field */
-    struct async_fileio *next;
-    HANDLE               handle;
-};
-
 struct async_fileio_read
 {
     struct async_fileio io;
diff --git a/dlls/ntdll/unix/server.c b/dlls/ntdll/unix/server.c
index d153fdce0be..10f53bea8ab 100644
--- a/dlls/ntdll/unix/server.c
+++ b/dlls/ntdll/unix/server.c
@@ -390,12 +390,12 @@ static void invoke_system_apc( const apc_call_t *call, apc_result_t *result, BOO
     case APC_ASYNC_IO:
     {
         IO_STATUS_BLOCK *iosb = wine_server_get_ptr( call->async_io.sb );
-        NTSTATUS (**user)(void *, IO_STATUS_BLOCK *, NTSTATUS) = wine_server_get_ptr( call->async_io.user );
+        struct async_fileio *user = wine_server_get_ptr( call->async_io.user );
         void *saved_frame = get_syscall_frame();
         void *frame;
 
         result->type = call->type;
-        result->async_io.status = (*user)( user, iosb, call->async_io.status );
+        result->async_io.status = user->callback( user, iosb, call->async_io.status );
 
         if ((frame = get_syscall_frame()) != saved_frame)
         {
diff --git a/dlls/ntdll/unix/unix_private.h b/dlls/ntdll/unix/unix_private.h
index bd00d4e9d42..3c23562b7a0 100644
--- a/dlls/ntdll/unix/unix_private.h
+++ b/dlls/ntdll/unix/unix_private.h
@@ -75,6 +75,15 @@ static inline struct ntdll_thread_data *ntdll_get_thread_data(void)
     return (struct ntdll_thread_data *)&NtCurrentTeb()->GdiTebBatch;
 }
 
+typedef NTSTATUS async_callback_t( void *user, IO_STATUS_BLOCK *io, NTSTATUS status );
+
+struct async_fileio
+{
+    async_callback_t    *callback;
+    struct async_fileio *next;
+    HANDLE               handle;
+};
+
 static const SIZE_T page_size = 0x1000;
 static const SIZE_T teb_size = 0x3000;  /* TEB64 + TEB32 */
 static const SIZE_T signal_stack_mask = 0xffff;