diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index 819d478..3f58f0d 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -2537,7 +2537,7 @@
         if not self.should_use_dyndeps_for_target(target):
             return
         extension = os.path.splitext(src.fname)[1][1:]
-        if not (extension in compilers.lang_suffixes['fortran'] or extension in compilers.lang_suffixes['cpp']):
+        if not (extension.lower() in compilers.lang_suffixes['fortran'] or extension in compilers.lang_suffixes['cpp']):
             return
         dep_scan_file = self.get_dep_scan_file_for(target)
         element.add_item('dyndep', dep_scan_file)
diff --git a/test cases/fortran/2 modules/meson.build b/test cases/fortran/2 modules/meson.build
index 791ae63..c9bfd8d 100644
--- a/test cases/fortran/2 modules/meson.build
+++ b/test cases/fortran/2 modules/meson.build
@@ -3,6 +3,7 @@
 
 commented = library('commented', 'comment_mod.f90')
 
-e = executable('modprog', 'mymod.f90', 'prog.f90',
+# Have one file with an upper case file extension.
+e = executable('modprog', 'mymod.F90', 'prog.f90',
   link_with: commented)
 test('moduletest', e)
diff --git a/test cases/fortran/2 modules/mymod.f90 b/test cases/fortran/2 modules/mymod.F90
similarity index 100%
rename from test cases/fortran/2 modules/mymod.f90
rename to test cases/fortran/2 modules/mymod.F90