diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index 00c6e6edb..5315ee6d9 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -34,4 +34,5 @@
 | thomasmelvin        | Thomas Melvin      | Met Office                       | 2026-01-15 |
 | tinyendian          | Wolfgang Hayek     | Earth Sciences New Zealand       | 2026-02-02 |
 | DanStoneMO          | Daniel Stone       | Met Office                       | 2026-02-26 |
-| ericaneininger      | Erica Neininger    | Met Office                       | 2026-03-02 |
\ No newline at end of file
+| ericaneininger      | Erica Neininger    | Met Office                       | 2026-03-02 |
+| iboutle             | Ian Boutle         | Met Office                       | 2026-03-04 |
diff --git a/interfaces/physics_schemes_interface/source/kernel/bl_imp_diag_kernel_mod.F90 b/interfaces/physics_schemes_interface/source/kernel/bl_imp_diag_kernel_mod.F90
index eaedaef19..a07f65a4b 100644
--- a/interfaces/physics_schemes_interface/source/kernel/bl_imp_diag_kernel_mod.F90
+++ b/interfaces/physics_schemes_interface/source/kernel/bl_imp_diag_kernel_mod.F90
@@ -97,17 +97,17 @@ subroutine bl_imp_diag_code(nlayers,                              &
     integer(i_def), intent(in) :: map_wth(ndf_wth)
     integer(i_def), intent(in) :: map_w3(ndf_w3)
     integer(i_def), intent(in) :: map_2d(ndf_2d)
-    real(r_def), intent(in) :: bt_bl(ndf_wth)
-    real(r_def), intent(in) :: bq_bl(ndf_wth)
-    real(r_def), intent(in) :: ftl(ndf_w3)
-    real(r_def), intent(in) :: fqw(ndf_w3)
-    real(r_def), intent(in) :: taux(ndf_w3)
-    real(r_def), intent(in) :: tauy(ndf_w3)
-    real(r_def), intent(in) :: wetrho_in_w3(ndf_w3)
-    real(r_def), intent(out) :: theta_star_surf(ndf_2d)
-    real(r_def), intent(out) :: qv_star_surf(ndf_2d)
-    real(r_def), intent(out) :: ustar_implicit(ndf_2d)
-    real(r_def), intent(in) :: zh(ndf_2d)
+    real(r_def), intent(in) :: bt_bl(undf_wth)
+    real(r_def), intent(in) :: bq_bl(undf_wth)
+    real(r_def), intent(in) :: ftl(undf_w3)
+    real(r_def), intent(in) :: fqw(undf_w3)
+    real(r_def), intent(in) :: taux(undf_w3)
+    real(r_def), intent(in) :: tauy(undf_w3)
+    real(r_def), intent(in) :: wetrho_in_w3(undf_w3)
+    real(r_def), intent(out) :: theta_star_surf(undf_2d)
+    real(r_def), intent(out) :: qv_star_surf(undf_2d)
+    real(r_def), intent(out) :: ustar_implicit(undf_2d)
+    real(r_def), intent(in) :: zh(undf_2d)
     real(r_def) :: taux_surf, tauy_surf, wm
     real(r_def) :: ftl_surf, fqw_surf, fb_surf
     real(r_def), parameter :: one_quarter = 1.0_r_def/4.0_r_def