Invalid timestep

Dear lammps users,
Do you have any idea that why this command:
fix dtem_out all ave/time 1 {nthermal} {nthermal} v_dtem

and nthermal=10000 leads to the below error?

ERROR: Invalid timestep reset for fix ave/time (…/fix_ave_time.cpp:578)

Best regards,
Nima Pirouzmand

Dear lammps users,
Do you have any idea that why this command:
fix dtem_out all ave/time 1 \{nthermal\} {nthermal} v_dtem

and nthermal=10000 leads to the below error?

ERROR: Invalid timestep reset for fix ave/time (../fix_ave_time.cpp:578)

​it doesn't. something else does cause this.

axel.​