diff --git a/build/Makefile b/build/Makefile
index 019f125a1..a780e1c0d 100644
--- a/build/Makefile
+++ b/build/Makefile
@@ -539,7 +539,7 @@ SOURCES= physcon.f90 ${CONFIG} ${SRCKERNEL} io.F90 units.f90 \
          readwrite_infile.F90 dens.F90 force.F90 deriv.F90 energies.F90 sort_particles.f90 \
          utils_shuffleparticles.F90 evwrite.f90 step_leapfrog.F90 writeheader.F90 ${SRCAN} step_supertimestep.F90 \
          mf_write.f90 evolve.F90 utils_orbits.f90 utils_linalg.f90 \
-         checksetup.F90 initial.F90
+         checksetup.f90 initial.F90
 
 # Needed as einsteintk_wrapper depends on initial
 ifeq ($(GR),yes)
diff --git a/build/Makefile_setups b/build/Makefile_setups
index ae562595d..85ccc0e0e 100644
--- a/build/Makefile_setups
+++ b/build/Makefile_setups
@@ -420,7 +420,7 @@ endif
 ifeq ($(SETUP), shock)
 #   shock tube tests
     PERIODIC=yes
-    SETUPFILE= setup_shock.F90
+    SETUPFILE= setup_shock.f90
     KERNEL=quintic
     KNOWN_SETUP=yes
 endif
@@ -428,7 +428,7 @@ endif
 ifeq ($(SETUP), dustyshock)
 #   shock tube tests with dust
     PERIODIC=yes
-    SETUPFILE= setup_shock.F90
+    SETUPFILE= setup_shock.f90
     DUST=yes
     KERNEL=quintic
     KNOWN_SETUP=yes
@@ -437,7 +437,7 @@ endif
 ifeq ($(SETUP), mhdshock)
 #   Ryu & Brio-Wu shock tube tests
     PERIODIC=yes
-    SETUPFILE= setup_shock.F90
+    SETUPFILE= setup_shock.f90
     MHD=yes
     KERNEL=quintic
     KNOWN_SETUP=yes
@@ -446,7 +446,7 @@ endif
 ifeq ($(SETUP), nimhdshock)
 #   non-ideal mhd standing and C shock tests
     PERIODIC=yes
-    SETUPFILE= setup_shock.F90
+    SETUPFILE= setup_shock.f90
     MHD=yes
     STS_TIMESTEPS=no
     NONIDEALMHD=yes
@@ -460,7 +460,7 @@ ifeq ($(SETUP), radshock)
 #   shock tube in radiation hydrodynamics
     PERIODIC=yes
     RADIATION=yes
-    SETUPFILE= setup_shock.F90
+    SETUPFILE= setup_shock.f90
     KERNEL=quintic
     KNOWN_SETUP=yes
 endif
@@ -468,7 +468,7 @@ endif
 ifeq ($(SETUP), srshock)
 #   special relativistic sod shock tube test
     PERIODIC=yes
-    SETUPFILE= setup_shock.F90
+    SETUPFILE= setup_shock.f90
     KERNEL=quintic
     GR=yes
     METRIC=minkowski
@@ -479,7 +479,7 @@ endif
 
 ifeq ($(SETUP), testparticles)
 #   test particles
-    SETUPFILE= setup_testparticles.F90
+    SETUPFILE= setup_testparticles.f90
     KNOWN_SETUP=yes
     MAXP=500000
     ANALYSIS= analysis_1particle.f90
@@ -1037,7 +1037,7 @@ ifeq ($(SETUP), testgr)
 endif
 
 ifeq ($(SETUP), flrw)
-#   constant density FLRW cosmology with perturbations  
+#   constant density FLRW cosmology with perturbations
     GR=yes
     KNOWN_SETUP=yes
     IND_TIMESTEPS=no
diff --git a/src/main/checksetup.F90 b/src/main/checksetup.f90
similarity index 100%
rename from src/main/checksetup.F90
rename to src/main/checksetup.f90
diff --git a/src/setup/setup_shock.F90 b/src/setup/setup_shock.f90
similarity index 100%
rename from src/setup/setup_shock.F90
rename to src/setup/setup_shock.f90
diff --git a/src/setup/setup_testparticles.F90 b/src/setup/setup_testparticles.f90
similarity index 100%
rename from src/setup/setup_testparticles.F90
rename to src/setup/setup_testparticles.f90
diff --git a/src/utils/interpolate3D.F90 b/src/utils/interpolate3D.f90
similarity index 98%
rename from src/utils/interpolate3D.F90
rename to src/utils/interpolate3D.f90
index 1a6d0d75e..95fe2d7d6 100644
--- a/src/utils/interpolate3D.F90
+++ b/src/utils/interpolate3D.f90
@@ -17,7 +17,7 @@ module interpolations3D
 ! :Dependencies: einsteintk_utils, kernel
 !
  use einsteintk_utils,  only:exact_rendering
- use kernel,       only:radkern2,radkern,cnormk,wkern
+ use kernel,            only:radkern2,radkern,cnormk,wkern
  implicit none
  integer, parameter :: doub_prec = kind(0.d0)
  real :: cnormk3D = cnormk
@@ -990,12 +990,12 @@ pure elemental real function soft_func(x,eps) result(f)
 
 end function soft_func
 
- !--------------------------------------------------------------------------
- !
- !  utility to wrap pixel index around periodic domain
- !  indices that roll beyond the last position are re-introduced at the first
- !
- !--------------------------------------------------------------------------
+!--------------------------------------------------------------------------
+!
+!  utility to wrap pixel index around periodic domain
+!  indices that roll beyond the last position are re-introduced at the first
+!
+!--------------------------------------------------------------------------
 pure integer function iroll(i,n)
  integer, intent(in) :: i,n
 
@@ -1008,5 +1008,5 @@ pure integer function iroll(i,n)
  endif
 
 end function iroll
-end module interpolations3D
 
+end module interpolations3D