diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 3505ef9..456c518 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -44,6 +44,12 @@ repos:
       - id: ruff
         args: [ --fix, --exit-non-zero-on-fix ]
       - id: ruff-format
+  - repo: https://github.com/PlasmaFAIR/fortitude-pre-commit
+    # Fortitude version.
+    rev: v0.7.5
+    hooks:
+      - id: fortitude
+        args: ["--fix", "--unsafe-fixes", "--preview"]
   - repo: https://github.com/astral-sh/uv-pre-commit
     rev: 0.5.21
     hooks:
diff --git a/changelog/28.trivial.md b/changelog/28.trivial.md
new file mode 100644
index 0000000..4a16b99
--- /dev/null
+++ b/changelog/28.trivial.md
@@ -0,0 +1 @@
+Added [fortitude](https://github.com/PlasmaFAIR/fortitude) for linting the Fortran
diff --git a/fortitude.toml b/fortitude.toml
new file mode 100644
index 0000000..2161fc4
--- /dev/null
+++ b/fortitude.toml
@@ -0,0 +1,5 @@
+[check]
+# TODO: think about adding other rules
+select = [ "C", "E", "S" ]
+ignore = [ ]
+line-length = 120
diff --git a/src/example_fgen_basic/get_wavelength.f90 b/src/example_fgen_basic/get_wavelength.f90
index abe43e4..7edbcf3 100644
--- a/src/example_fgen_basic/get_wavelength.f90
+++ b/src/example_fgen_basic/get_wavelength.f90
@@ -7,7 +7,7 @@ module m_get_wavelength
 
     use kind_parameters, only: dp
 
-    implicit none
+    implicit none (type, external)
     private
 
     real(kind=dp), parameter, public :: speed_of_light = 2.99792e8_dp
diff --git a/src/example_fgen_basic/get_wavelength_wrapper.f90 b/src/example_fgen_basic/get_wavelength_wrapper.f90
index c983c12..8aa3b49 100644
--- a/src/example_fgen_basic/get_wavelength_wrapper.f90
+++ b/src/example_fgen_basic/get_wavelength_wrapper.f90
@@ -15,7 +15,7 @@ module m_get_wavelength_w  ! Convention to date: just suffix wrappers with _w
     ! and the original function should have the same name.
     ! ("o_" for original)
 
-    implicit none
+    implicit none (type, external)
     private
 
     public :: get_wavelength
diff --git a/src/example_fgen_basic/kind_parameters.f90 b/src/example_fgen_basic/kind_parameters.f90
index ffc60b0..4e7378e 100644
--- a/src/example_fgen_basic/kind_parameters.f90
+++ b/src/example_fgen_basic/kind_parameters.f90
@@ -2,23 +2,23 @@
 !> See https://fortran-lang.org/learn/best_practices/floating_point/
 module kind_parameters
 
-    implicit none
-    public
+    implicit none (type, external)
+    private
 
     !> Single precision real numbers, 6 digits, range 10⁻³⁷ to 10³⁷-1; 32 bits
-    integer, parameter :: sp = selected_real_kind(6, 37)
+    integer, parameter, public :: sp = selected_real_kind(6, 37)
     !> Double precision real numbers, 15 digits, range 10⁻³⁰⁷ to 10³⁰⁷-1; 64 bits
-    integer, parameter :: dp = selected_real_kind(15, 307)
+    integer, parameter, public :: dp = selected_real_kind(15, 307)
     !> Quadruple precision real numbers, 33 digits, range 10⁻⁴⁹³¹ to 10⁴⁹³¹-1; 128 bits
-    integer, parameter :: qp = selected_real_kind(33, 4931)
+    integer, parameter, public :: qp = selected_real_kind(33, 4931)
 
     !> Char length for integers, range -2⁷ to 2⁷-1; 8 bits
-    integer, parameter :: i1 = selected_int_kind(2)
+    integer, parameter, public :: i1 = selected_int_kind(2)
     !> Short length for integers, range -2¹⁵ to 2¹⁵-1; 16 bits
-    integer, parameter :: i2 = selected_int_kind(4)
+    integer, parameter, public :: i2 = selected_int_kind(4)
     !> Length of default integers, range -2³¹ to 2³¹-1; 32 bits
-    integer, parameter :: i4 = selected_int_kind(9)
+    integer, parameter, public :: i4 = selected_int_kind(9)
     !> Long length for integers, range -2⁶³ to 2⁶³-1; 64 bits
-    integer, parameter :: i8 = selected_int_kind(18)
+    integer, parameter, public :: i8 = selected_int_kind(18)
 
 end module kind_parameters
diff --git a/tests/unit/main.f90 b/tests/unit/main.f90
index 5f4d22f..b63d95b 100644
--- a/tests/unit/main.f90
+++ b/tests/unit/main.f90
@@ -5,7 +5,7 @@ program tester_unit
     use testdrive, only: run_testsuite, new_testsuite, testsuite_type, select_suite, run_selected, get_argument
     use test_get_wavelength, only: collect_get_wavelength_tests
 
-    implicit none
+    implicit none (type, external)
     integer :: stat, is
     character(len=:), allocatable :: suite_name, test_name
     type(testsuite_type), allocatable :: testsuites(:)
@@ -47,7 +47,7 @@ program tester_unit
     end if
 
     if (stat > 0) then
-        write (error_unit, '(i0, 1x, a)') stat, "test(s) failed!"
+        write (error_unit, "(i0, 1x, a)") stat, "test(s) failed!"
         error stop 1
     end if
 
diff --git a/tests/unit/test_get_wavelength.f90 b/tests/unit/test_get_wavelength.f90
index 99cba3f..d69c1b1 100644
--- a/tests/unit/test_get_wavelength.f90
+++ b/tests/unit/test_get_wavelength.f90
@@ -2,12 +2,12 @@
 module test_get_wavelength
 
     ! How to print to stdout
-    use ISO_Fortran_env, only: stdout => OUTPUT_UNIT
+    use, intrinsic :: ISO_Fortran_env, only: stdout => OUTPUT_UNIT
     use testdrive, only: new_unittest, unittest_type, error_type, check
 
     use kind_parameters, only: dp
 
-    implicit none
+    implicit none (type, external)
     private
 
     public :: collect_get_wavelength_tests