dosemu crashes with fcomip

dosemu-1.4.0.1
Suse Linux 15.1
uname -a => Linux linux-71lv 4.12.14-lp151.28.48-default #1 SMP Fri Apr 17 05:38:36 UTC 2020 (18849d1) x86_64 x86_64 x86_64 GNU/Linux

I try to replace an old library module (real-number computing, the old one without FPU support) for FST Modula-2 compiler (that does "not" work under DOSEMU, so I did it in real drdos). Everything went fine until I tried to compare the output of a test program to bc results (i.e. I ran the program under DOSEMU): The program crashed, and with some debugguing I found out the offending instruction was

"ESC 3DH,CX" in the source-code (8086 instructions only!)
aka FCOMIP ST,ST(1)
or DF, E9 in binary code.

I can't see any hint in the AMD manual that this instruction does not work in virtual mode, it works in real mode, so why does dosemu crash with
ERROR: EMU86: error 96
?

I tried fiddling with $FPU (on/off), with no effect. Is there a feature in deosemu.conf or elsewhere that I should change? Or is it a bug in DOSEMU?

PS: Couldn't find out whether 1 or 9 is highest Priority, so I did not lower the priority of this ticket.