#305 SET PENDING from within a prefix macro fails.

[z/VMphile]

I'm writing an emulation of the CMS XEDIT SI macro, which needs to set a new instance of itself on the currently added line if its content is non-blank; but when I issue 'command set pending on newname' in the macro, THE returns 'Invalid prefix synonym newname' and prefixes its name with ? in the prefix area.
I attach my profile.the and pfxSI.the for review.