diff --git a/src/phase_mechanical.f90 b/src/phase_mechanical.f90
index 37e6fe7bf..1917d81c9 100644
--- a/src/phase_mechanical.f90
+++ b/src/phase_mechanical.f90
@@ -168,17 +168,17 @@ submodule(phase) mechanical
       integer,     intent(in) :: ph,en
     end function plastic_dislotwin_homogenizedC
 
-    module function elastic_C66(ph,en) result(C66)
+    pure module function elastic_C66(ph,en) result(C66)
       real(pReal), dimension(6,6) :: C66
       integer,     intent(in) :: ph, en
     end function elastic_C66
 
-    module function elastic_mu(ph,en) result(mu)
+    pure module function elastic_mu(ph,en) result(mu)
       real(pReal) :: mu
       integer, intent(in) :: ph, en
     end function elastic_mu
 
-    module function elastic_nu(ph,en) result(nu)
+    pure module function elastic_nu(ph,en) result(nu)
       real(pReal) :: nu
       integer, intent(in) :: ph, en
     end function elastic_nu
diff --git a/src/phase_mechanical_elastic.f90 b/src/phase_mechanical_elastic.f90
index acbbac236..24797a880 100644
--- a/src/phase_mechanical_elastic.f90
+++ b/src/phase_mechanical_elastic.f90
@@ -86,7 +86,7 @@ end subroutine elastic_init
 !--------------------------------------------------------------------------------------------------
 !> @brief return 6x6 elasticity tensor
 !--------------------------------------------------------------------------------------------------
-module function elastic_C66(ph,en) result(C66)
+pure module function elastic_C66(ph,en) result(C66)
 
   integer, intent(in) :: &
     ph, &
@@ -140,7 +140,7 @@ end function elastic_C66
 !--------------------------------------------------------------------------------------------------
 !> @brief return shear modulus
 !--------------------------------------------------------------------------------------------------
-module function elastic_mu(ph,en) result(mu)
+pure module function elastic_mu(ph,en) result(mu)
 
   integer, intent(in) :: &
     ph, &
@@ -157,7 +157,7 @@ end function elastic_mu
 !--------------------------------------------------------------------------------------------------
 !> @brief return Poisson ratio
 !--------------------------------------------------------------------------------------------------
-module function elastic_nu(ph,en) result(nu)
+pure module function elastic_nu(ph,en) result(nu)
 
   integer, intent(in) :: &
     ph, &