Transforming tracts from MNI to T1

I’m currently trying to transform a tck file from MNI-space to T1_subject-space. I’ve been reading a lot of others people problems on this topic but none is helping me out. I already have calculated the MNI_to_T1_warp_coef.nii.gz of my subject but when using tcktransform, the tracts are not located right. This is my current code:

warpconvert MNI_to_T1_warp_coef.nii.gz displacement2deformation MNI_to_T1_def.nii.gz
warpinvert MNI_to_T1_def.nii.gz MNI_to_T1_def_inv.nii.gz
tcktransform AF_all_LT_GN_symmetrical.tck MNI_to_T1_def_inv.nii.gz AF_all_LT_GN_symmetrical_T1.tck

Can someone help me out please?
Thanks in advance!