[gmx-users] g_wham error in umbrella simulation

[diana p]

Dear all
I am doing an umbrella simulation by using the pull code in Gromacs
4.6.5 to calculate the PMF. The pull parameters are the following:

;Pull code
pull                    = constant_force
pull_geometry  = position
pull_dim            = N N Ypull_start           = no
pull_ngroups     = 1pull_group0       = GRApull_group1       =
UNKpull_rate1          = 0.01     pull_k1              = 1000
pull_vec1          = 0.0 0.0 1.0

When i run the WHAM with the Command line:
g_wham -it tpr-files.dat -if pullf-files.dat -o -hist -unit kCal
it gave me the following error:

Fatal error: This is not a tpr of an umbrella simulation. Found pull type
"constant-force" (ir.ePull= 3)

I would be more than pleased if someone could guid me.
Thank You in advance