DDE: Fatal internal error: gendcI(2,1)

Source code:
typedef struct {
char Reason;
__packed short X,Y;
} t_OSWord21;

char Name[] = “Test”;
t_OSWord21 Mouse;

Run this through DDE C results in this error:

Norcroft RISC OS Arm C vsn 5.89 [18 Feb 2022]
“c.test”, line 8: Fatal internal error: gendcI(2,1)

Internal inconsistency: either resource shortage or compiler fault. If you
cannot alter your program to avoid this failure, please contact your supplier

Note that when I define a t_OSWord21 thingy inside a function it does work just fine… just outside as global the compiler fails on me.