diff --git a/configure b/configure
index 5a4eba53..8fd223c0 100755
--- a/configure
+++ b/configure
@@ -1808,7 +1808,12 @@ if test "$enable_debug" == "yes"
 then
   debug_nag='-C=all -gline -nan'
   debug_ifort='-check all -warn all -warn nodec -warn interfaces -gen_interfaces -traceback -g'
-  debug_gfortran='-Wall -fbounds-check -g'
+  # Unused dummy arguments are not warned about because many procedures have
+  # to conform to interfaces shared between the different grid geometries,
+  # and unused functions are not warned about because some private library
+  # functions are intentionally unused (including empty contained subroutines
+  # that work around a PGI compiler bug).
+  debug_gfortran='-Wall -Wno-unused-dummy-argument -Wno-unused-function -fbounds-check -g'
   debug_g95='-Wall -fbounds-check -g'
   debug_pgi='-Mbounds -traceback -g'
 else
diff --git a/configure.ac b/configure.ac
index 54349bf9..4c00ab88 100644
--- a/configure.ac
+++ b/configure.ac
@@ -49,7 +49,12 @@ if test "$enable_debug" == "yes"
 then
   debug_nag='-C=all -gline -nan'
   debug_ifort='-check all -warn all -warn nodec -warn interfaces -gen_interfaces -traceback -g'
-  debug_gfortran='-Wall -fbounds-check -g'
+  # Unused dummy arguments are not warned about because many procedures have
+  # to conform to interfaces shared between the different grid geometries,
+  # and unused functions are not warned about because some private library
+  # functions are intentionally unused (including empty contained subroutines
+  # that work around a PGI compiler bug).
+  debug_gfortran='-Wall -Wno-unused-dummy-argument -Wno-unused-function -fbounds-check -g'
   debug_g95='-Wall -fbounds-check -g'
   debug_pgi='-Mbounds -traceback -g'
 else
diff --git a/fortranlib b/fortranlib
index d34e82fc..60fd094d 160000
--- a/fortranlib
+++ b/fortranlib
@@ -1 +1 @@
-Subproject commit d34e82fcfa77be7d48cfde31fd8d7df2d7346f12
+Subproject commit 60fd094d3e137137ce00ec120b085e9b23ebf68b
diff --git a/src/dust/dust_type_4elem.f90 b/src/dust/dust_type_4elem.f90
index 61722d0c..5558f513 100644
--- a/src/dust/dust_type_4elem.f90
+++ b/src/dust/dust_type_4elem.f90
@@ -87,7 +87,6 @@ subroutine dust_setup(group,d,beta)
     character(len=100) :: path
     character(len=4) :: sublimation
     type(version) :: python_version
-    integer :: dust_version
 
     ! Read dust file
 
diff --git a/src/grid/grid_geometry_cylindrical_3d.f90 b/src/grid/grid_geometry_cylindrical_3d.f90
index 0dd5ae33..ada3f35f 100644
--- a/src/grid/grid_geometry_cylindrical_3d.f90
+++ b/src/grid/grid_geometry_cylindrical_3d.f90
@@ -444,7 +444,7 @@ logical function in_correct_cell(p)
 
     type(photon),intent(in) :: p
     type(grid_cell) :: icell_actual
-    real(dp) :: phi,frac,dphi,r_sq,w_sq
+    real(dp) :: phi,frac,dphi,w_sq
     real(dp),parameter :: threshold = 1.e-3_dp
 
     icell_actual = find_cell(p)
diff --git a/src/grid/grid_geometry_octree.f90 b/src/grid/grid_geometry_octree.f90
index 4a9ac5f8..696dda86 100644
--- a/src/grid/grid_geometry_octree.f90
+++ b/src/grid/grid_geometry_octree.f90
@@ -194,7 +194,6 @@ subroutine setup_grid_geometry(group)
 
     integer(hid_t),intent(in) :: group
 
-    real(dp) :: x, y, z, dx, dy, dz
     integer :: ic, iv
 
     ! FIX - issue with reading 64-bit 1D column with 32-bit variables
@@ -370,7 +369,6 @@ end function next_cell_wall_id
   logical function in_correct_cell(p)
     implicit none
     type(photon),intent(in) :: p
-    type(grid_cell) :: curr
     type(grid_cell) :: icell_actual
     real(dp) :: frac,frac1, frac2, frac3
     icell_actual = find_cell(p)
diff --git a/src/grid/grid_geometry_voronoi.f90 b/src/grid/grid_geometry_voronoi.f90
index 6af303fc..a3402064 100644
--- a/src/grid/grid_geometry_voronoi.f90
+++ b/src/grid/grid_geometry_voronoi.f90
@@ -45,7 +45,6 @@ module grid_geometry_specific
   public :: setup_grid_geometry
   type(grid_geometry_desc),public,target :: geo
 
-  integer :: n_filled = 0
 
   ! Declare here otherwise pointer becomes corrupt
   real(dp),allocatable, target :: points(:,:)
@@ -103,7 +102,6 @@ subroutine setup_grid_geometry(group)
     real(dp), allocatable :: x(:), y(:), z(:)
     integer, allocatable :: sparse_neighs(:), sparse_idx(:)
     real(dp),allocatable :: bb_min(:,:), bb_max(:,:)
-    type(cell),pointer :: c
 
     ! Read geometry file
     call mp_read_keyword(group, '.', "geometry", geo%id)
@@ -261,8 +259,6 @@ recursive type(grid_cell) function next_cell_int(cell, direction, intersection)
     type(grid_cell),intent(in) :: cell
     integer,intent(in) :: direction
     type(vector3d_dp),optional,intent(in) :: intersection
-    type(grid_cell) :: parent_cell
-    integer :: subcell_id
     ! wall ID = cell ID
     c = new_grid_cell(direction, geo)
   end function next_cell_int
@@ -278,9 +274,6 @@ end function next_cell_wall_id
   logical function in_correct_cell(p)
     implicit none
     type(photon),intent(in) :: p
-    type(grid_cell) :: curr
-    type(grid_cell) :: icell_actual
-    real(dp) :: frac,frac1, frac2, frac3
     real(dp) :: point(3)
     type(kdtree2_result) :: results(2)
     ! TODO - only check the second result if it's close to the first
@@ -293,7 +286,6 @@ subroutine random_position_cell(icell,pos)
     implicit none
     type(grid_cell),intent(in) :: icell
     type(vector3d_dp), intent(out) :: pos
-    type(grid_cell) :: icell_actual
 
     type(kdtree2_result) :: results(1)
     real(dp) :: point(3)
@@ -322,8 +314,8 @@ end subroutine random_position_cell
   real(dp) function distance_to_closest_wall(p) result(d)
     implicit none
     type(photon),intent(in) :: p
-    real(dp) :: d1,d2,d3,d4,d5,d6
     call error("distance_to_closest_wall", "not implemented for Voronoi grid")
+    d = 0._dp
     ! TODO: is this the second nearest neighbor?
   end function distance_to_closest_wall
 
@@ -346,8 +338,8 @@ subroutine find_wall(p,radial,tmin,id_min)
 
 
     integer :: i, n_neighbors
-    type(vector3d_dp) :: r0, ri, rmid, n
-    real(dp) :: t, tx, ty, tz
+    type(vector3d_dp) :: rmid, n
+    real(dp) :: t
 
 
     icell => geo%cells(p%icell%ic)
diff --git a/src/grid/grid_mrw_3d.f90 b/src/grid/grid_mrw_3d.f90
index e3ec2c79..6a6e4d26 100644
--- a/src/grid/grid_mrw_3d.f90
+++ b/src/grid/grid_mrw_3d.f90
@@ -18,7 +18,6 @@ module grid_mrw
   public :: grid_do_mrw_noenergy
   public :: mrw_peeloff
 
-  logical :: debug = .false.
 
   integer,parameter :: ncdf = 100
   real(dp) :: xcdf(ncdf), ycdf(ncdf)
diff --git a/src/grid/grid_physics_3d.f90 b/src/grid/grid_physics_3d.f90
index c3ce4948..6cd0249b 100644
--- a/src/grid/grid_physics_3d.f90
+++ b/src/grid/grid_physics_3d.f90
@@ -61,7 +61,6 @@ module grid_physics
   integer :: id
   integer :: idx 
 
-  logical :: debug = .false.
 
   type(pdf_discrete_dp) :: absorption
 
diff --git a/src/images/image_type.f90 b/src/images/image_type.f90
index ccd6e5ba..558fb82b 100644
--- a/src/images/image_type.f90
+++ b/src/images/image_type.f90
@@ -163,7 +163,7 @@ subroutine image_setup(handle,path,img,n_view,n_sources,n_dust,use_exact_nu,freq
     real(dp) :: wav_min, wav_max
     integer :: io_bytes
     logical :: compute_stokes
-    integer :: ig, n_filt
+    integer :: ig
     character(len=100) :: group_name
 
     img%n_view = n_view
diff --git a/src/main/iter_final.f90 b/src/main/iter_final.f90
index 58f175db..38d86c88 100644
--- a/src/main/iter_final.f90
+++ b/src/main/iter_final.f90
@@ -68,7 +68,7 @@ subroutine do_final(n_photons_tot,n_photons_chunk,peeloff_scattering_only)
     integer(idp) :: n_photons, n_photons_curr
 
     ! Photon object and variable to loop over photons
-    integer :: ip
+    integer(idp) :: ip
     type(photon) :: p
 
     ! Whether to only peeloff scattered photons
@@ -153,10 +153,10 @@ subroutine propagate(p,peeloff_scattering_only)
     integer(idp) :: interactions
     real(dp) :: tau_achieved, tau, tau_escape
     type(photon) :: p_tmp
-    real(dp) :: xi, weight
+    real(dp) :: weight
     logical :: killed
-    integer :: mrw_steps
-    integer :: ia
+    integer(idp) :: mrw_steps
+    integer(idp) :: ia
 
     ! Propagate photon
     do interactions=1, n_inter_max+1
diff --git a/src/main/iter_final_mono.f90 b/src/main/iter_final_mono.f90
index d35dd18f..b5e3fe20 100644
--- a/src/main/iter_final_mono.f90
+++ b/src/main/iter_final_mono.f90
@@ -69,7 +69,7 @@ subroutine do_final_mono(n_photons_sources,n_photons_thermal,n_photons_chunk, pe
     integer(idp) :: n_photons, n_photons_curr
 
     ! Photon object and variable to loop over photons
-    integer :: ip
+    integer(idp) :: ip
     type(photon) :: p
 
     integer :: inu
@@ -237,9 +237,9 @@ subroutine propagate(p)
     integer(idp) :: interactions
     real(dp) :: tau_achieved, tau, tau_escape
     type(photon) :: p_tmp
-    real(dp) :: xi, weight
+    real(dp) :: weight
     logical :: killed
-    integer :: ia
+    integer(idp) :: ia
 
     logical, parameter :: force_scatter = .true.
     real(dp) :: energy_initial
diff --git a/src/main/iter_lucy.f90 b/src/main/iter_lucy.f90
index 5778ce52..dd7cbeb0 100644
--- a/src/main/iter_lucy.f90
+++ b/src/main/iter_lucy.f90
@@ -74,11 +74,11 @@ subroutine do_lucy(n_photons_tot,n_photons_chunk)
     integer(idp) :: n_photons, n_photons_curr
 
     ! Photon object and variable to loop over photons
-    integer :: ip, ia
+    integer(idp) :: ip, ia
     type(photon) :: p
 
     ! Number of interactions
-    integer :: interactions,mrw_steps
+    integer(idp) :: interactions,mrw_steps
 
     ! Optical depth to travel
     real(dp) :: tau
diff --git a/src/main/iter_raytracing.f90 b/src/main/iter_raytracing.f90
index bc998ff2..2a629436 100644
--- a/src/main/iter_raytracing.f90
+++ b/src/main/iter_raytracing.f90
@@ -39,7 +39,7 @@ subroutine do_raytracing(n_photons_sources,n_photons_thermal,n_photons_chunk)
     integer(idp) :: n_photons, n_photons_curr
 
     ! Photon object and variable to loop over photons
-    integer :: ip
+    integer(idp) :: ip
     type(photon) :: p
 
     n_photons_curr = 0