diff --git a/server/console.c b/server/console.c
index 0080e6ed163..df88b14f609 100644
--- a/server/console.c
+++ b/server/console.c
@@ -101,7 +101,7 @@ static enum server_fd_type console_get_fd_type( struct fd *fd );
 static void console_get_file_info( struct fd *fd, obj_handle_t handle, unsigned int info_class );
 static void console_get_volume_info( struct fd *fd, struct async *async, unsigned int info_class );
 static void console_read( struct fd *fd, struct async *async, file_pos_t pos );
-static int console_flush( struct fd *fd, struct async *async );
+static void console_flush( struct fd *fd, struct async *async );
 static int console_ioctl( struct fd *fd, ioctl_code_t code, struct async *async );
 
 static const struct fd_ops console_fd_ops =
@@ -326,7 +326,7 @@ static const struct object_ops console_input_ops =
 };
 
 static void console_input_read( struct fd *fd, struct async *async, file_pos_t pos );
-static int console_input_flush( struct fd *fd, struct async *async );
+static void console_input_flush( struct fd *fd, struct async *async );
 static int console_input_ioctl( struct fd *fd, ioctl_code_t code, struct async *async );
 
 static const struct fd_ops console_input_fd_ops =
@@ -960,16 +960,16 @@ static void console_read( struct fd *fd, struct async *async, file_pos_t pos )
     queue_host_ioctl( console->server, IOCTL_CONDRV_READ_FILE, 0, async, &console->ioctl_q );
 }
 
-static int console_flush( struct fd *fd, struct async *async )
+static void console_flush( struct fd *fd, struct async *async )
 {
     struct console *console = get_fd_user( fd );
 
     if (!console->server)
     {
         set_error( STATUS_INVALID_HANDLE );
-        return 0;
+        return;
     }
-    return queue_host_ioctl( console->server, IOCTL_CONDRV_FLUSH, 0, NULL, NULL );
+    queue_host_ioctl( console->server, IOCTL_CONDRV_FLUSH, 0, NULL, NULL );
 }
 
 static void screen_buffer_write( struct fd *fd, struct async *async, file_pos_t pos )
@@ -1361,16 +1361,16 @@ static void console_input_read( struct fd *fd, struct async *async, file_pos_t p
     console_read( console->fd, async, pos );
 }
 
-static int console_input_flush( struct fd *fd, struct async *async )
+static void console_input_flush( struct fd *fd, struct async *async )
 {
     struct console *console = current->process->console;
 
     if (!console)
     {
         set_error( STATUS_INVALID_HANDLE );
-        return 0;
+        return;
     }
-    return console_flush( console->fd, async );
+    console_flush( console->fd, async );
 }
 
 static void console_output_dump( struct object *obj, int verbose )
diff --git a/server/device.c b/server/device.c
index cc3e0466468..7e9954a9305 100644
--- a/server/device.c
+++ b/server/device.c
@@ -203,7 +203,7 @@ static void device_file_destroy( struct object *obj );
 static enum server_fd_type device_file_get_fd_type( struct fd *fd );
 static void device_file_read( struct fd *fd, struct async *async, file_pos_t pos );
 static void device_file_write( struct fd *fd, struct async *async, file_pos_t pos );
-static int device_file_flush( struct fd *fd, struct async *async );
+static void device_file_flush( struct fd *fd, struct async *async );
 static int device_file_ioctl( struct fd *fd, ioctl_code_t code, struct async *async );
 static void device_file_reselect_async( struct fd *fd, struct async_queue *queue );
 static void device_file_get_volume_info( struct fd *fd, struct async *async, unsigned int info_class );
@@ -649,14 +649,14 @@ static void device_file_write( struct fd *fd, struct async *async, file_pos_t po
     queue_irp( file, &params, async );
 }
 
-static int device_file_flush( struct fd *fd, struct async *async )
+static void device_file_flush( struct fd *fd, struct async *async )
 {
     struct device_file *file = get_fd_user( fd );
     irp_params_t params;
 
     memset( &params, 0, sizeof(params) );
     params.flush.type = IRP_CALL_FLUSH;
-    return queue_irp( file, &params, async );
+    queue_irp( file, &params, async );
 }
 
 static int device_file_ioctl( struct fd *fd, ioctl_code_t code, struct async *async )
diff --git a/server/fd.c b/server/fd.c
index 6b79585147d..ca91ff724a1 100644
--- a/server/fd.c
+++ b/server/fd.c
@@ -2304,10 +2304,9 @@ void no_fd_write( struct fd *fd, struct async *async, file_pos_t pos )
 }
 
 /* default flush() routine */
-int no_fd_flush( struct fd *fd, struct async *async )
+void no_fd_flush( struct fd *fd, struct async *async )
 {
     set_error( STATUS_OBJECT_TYPE_MISMATCH );
-    return 0;
 }
 
 /* default get_file_info() routine */
diff --git a/server/file.h b/server/file.h
index e200281d03b..c4c33fc1e79 100644
--- a/server/file.h
+++ b/server/file.h
@@ -61,7 +61,7 @@ struct fd_ops
     /* perform a write on the file */
     void (*write)(struct fd *, struct async *, file_pos_t );
     /* flush the object buffers */
-    int (*flush)(struct fd *, struct async *);
+    void (*flush)(struct fd *, struct async *);
     /* query file info */
     void (*get_file_info)( struct fd *, obj_handle_t, unsigned int );
     /* query volume info */
@@ -111,7 +111,7 @@ extern void fd_async_wake_up( struct fd *fd, int type, unsigned int status );
 extern void fd_reselect_async( struct fd *fd, struct async_queue *queue );
 extern void no_fd_read( struct fd *fd, struct async *async, file_pos_t pos );
 extern void no_fd_write( struct fd *fd, struct async *async, file_pos_t pos );
-extern int no_fd_flush( struct fd *fd, struct async *async );
+extern void no_fd_flush( struct fd *fd, struct async *async );
 extern void no_fd_get_file_info( struct fd *fd, obj_handle_t handle, unsigned int info_class );
 extern void default_fd_get_file_info( struct fd *fd, obj_handle_t handle, unsigned int info_class );
 extern void no_fd_get_volume_info( struct fd *fd, struct async *async, unsigned int info_class );
diff --git a/server/named_pipe.c b/server/named_pipe.c
index 503dda93931..3d1b2d8b917 100644
--- a/server/named_pipe.c
+++ b/server/named_pipe.c
@@ -145,7 +145,7 @@ static int pipe_end_set_sd( struct object *obj, const struct security_descriptor
 static WCHAR *pipe_end_get_full_name( struct object *obj, data_size_t *len );
 static void pipe_end_read( struct fd *fd, struct async *async, file_pos_t pos );
 static void pipe_end_write( struct fd *fd, struct async *async_data, file_pos_t pos );
-static int pipe_end_flush( struct fd *fd, struct async *async );
+static void pipe_end_flush( struct fd *fd, struct async *async );
 static void pipe_end_get_volume_info( struct fd *fd, struct async *async, unsigned int info_class );
 static void pipe_end_reselect_async( struct fd *fd, struct async_queue *queue );
 static void pipe_end_get_file_info( struct fd *fd, obj_handle_t handle, unsigned int info_class );
@@ -578,14 +578,14 @@ static void named_pipe_device_file_destroy( struct object *obj )
     release_object( file->device );
 }
 
-static int pipe_end_flush( struct fd *fd, struct async *async )
+static void pipe_end_flush( struct fd *fd, struct async *async )
 {
     struct pipe_end *pipe_end = get_fd_user( fd );
 
     if (!pipe_end->pipe)
     {
         set_error( STATUS_PIPE_DISCONNECTED );
-        return 0;
+        return;
     }
 
     if (pipe_end->connection && !list_empty( &pipe_end->connection->message_queue ))
@@ -593,7 +593,6 @@ static int pipe_end_flush( struct fd *fd, struct async *async )
         fd_queue_async( pipe_end->fd, async, ASYNC_TYPE_WAIT );
         set_error( STATUS_PENDING );
     }
-    return 1;
 }
 
 static void pipe_end_get_file_info( struct fd *fd, obj_handle_t handle, unsigned int info_class )