[fpc-pascal]Error: The object arg1 has no VMT

[Preben Mikael Bohn]

Dear all, I get the error "Error: The object TINTERPOLATION has no VMT" when
trying to compile one of my programs with the option -Sd (delphi mode), but
not in normal mode. The error is listed but apparently not documented in
http://www.freepascal.org/docs-html/user/node15.html#SECTION001510000000000000000
so can anyone help me out on this one?

Best regards Preben