diff --git a/code/constitutive_dislotwin.f90 b/code/constitutive_dislotwin.f90
index a9be85065..62bb872de 100644
--- a/code/constitutive_dislotwin.f90
+++ b/code/constitutive_dislotwin.f90
@@ -648,7 +648,7 @@ do i = 1_pInt,maxNinstance
              lattice_Qtwin(o,s,index_otherFamily+j,myStructure)
          enddo ; enddo ; enddo ; enddo
        enddo ; enddo ; enddo ; enddo
-       constitutive_dislotwin_Ctwin_66(:,:,k,i) = math_Mandel3333to66(constitutive_dislotwin_Ctwin_3333(:,:,:,:,k,i))
+       constitutive_dislotwin_Ctwin_66(:,:,index_myFamily+j,i) = math_Mandel3333to66(constitutive_dislotwin_Ctwin_3333(:,:,:,:,index_myFamily+j,i))
 
     !* Interaction matrices