diff --git a/README.markdown b/README.markdown
index f79dca0..eb298cc 100644
--- a/README.markdown
+++ b/README.markdown
@@ -301,6 +301,13 @@ following to your vimrc:
 + `<LocalLeader>D` : Move completed tasks to done file, see [TodoTxt
 Files](#todotxt-files)
 
+When you mark an item with a priority as done, it is assigned a priority tag
+like `pri:A` so that the priority can be restored if the item is toggled back
+to undone. If you don't want the tags showing up in your done file, you can
+disable this behavior by setting the following global variable:
+
+    let g:TodoTxtStripDoneItemPriority=1
+
 ### Format
 
 + `<LocalLeader>ff` : Try to fix todo.txt format
diff --git a/doc/todo.txt b/doc/todo.txt
index c58ef96..9aab494 100644
--- a/doc/todo.txt
+++ b/doc/todo.txt
@@ -328,6 +328,14 @@ following to your vimrc:
 
 `<LocalLeader>` is \ by default, so ̀`<LocaLeader>-s` means you type \s
 
+When you mark an item with a priority as done, it is assigned a priority tag
+like `pri:A` so that the priority can be restored if the item is toggled back
+to undone. If you don't want the tags showing up in your done file, you can
+disable this behavior by setting the following global variable:
+>
+    let g:TodoTxtStripDoneItemPriority=1
+<
+
 7.5 Format                                                     *TodoTxt-format*
 
     `<LocalLeader>ff` : Try to fix todo.txt format