diff --git a/src/crystal.f90 b/src/crystal.f90
index 33ca4dc74..7bf9dc2f7 100644
--- a/src/crystal.f90
+++ b/src/crystal.f90
@@ -2249,6 +2249,12 @@ subroutine crystal_selfTest
   CoSy   = buildCoordinateSystem([1],[1],system,'cF',0.0_pREAL)
   if (any(dNeq(CoSy(1:3,1:3,1),math_I3))) error stop 'buildCoordinateSystem'
 
+  if (any(dNeq(buildCoordinateSystem(TI_NSLIPSYSTEM,TI_NSLIPSYSTEM,TI_SYSTEMSLIP,'cI',0.0_pReal), &
+               buildCoordinateSystem(TI_NSLIPSYSTEM,TI_NSLIPSYSTEM,TI_SYSTEMSLIP,'tI',1.0_pReal)))) &
+                                                           error stop 'cI/tI coordinate system'
+  if (all(dEq( buildCoordinateSystem(TI_NSLIPSYSTEM,TI_NSLIPSYSTEM,TI_SYSTEMSLIP,'tI',1.1_pReal + r(1)*0.9_pReal), &
+               buildCoordinateSystem(TI_NSLIPSYSTEM,TI_NSLIPSYSTEM,TI_SYSTEMSLIP,'tI',1.0_pReal)))) &
+                                                           error stop 'tI coordinate system'
   do i = 1, 10
     call random_number(C)
     C_cF = crystal_symmetrize_C66(C,'cI')