Xwiki syntax to include document make edit form unable to edit again

Xwiki Syntax page give an example about document include:
#\includeTopic("Doc.TestInclude")
#\includeForm("Doc.TestInclude")
that has result:
Nom du document: TestInclude
Nom du document: XWikiSyntax
After I copy the above example to my test page then save, it make my test page unable to be edited again.
In another test page, try to remove '\' sign then save.
It still remain (There's no text field or text area in edit form so I cannot edit this page).
But there's small difference:
In the old page it show the text: "#includeTopic("Doc.TestInclude") #includeForm("Doc.TestInclude")".
In the new one it hasn't got that text.