diff --git a/bfps/DNS.py b/bfps/DNS.py
index be0ba7646ae8d64439e82d632ec82c2f40b2c32a..f9cf92c47cb7b7db1e2d82714def0c5a41d2cb86 100644
--- a/bfps/DNS.py
+++ b/bfps/DNS.py
@@ -916,7 +916,7 @@ class DNS(_code):
                             species = 0,
                             rseed = opt.particle_rand_seed)
                     if not os.path.exists(self.get_particle_file_name()):
-                        with particle_file = h5py.File(self.get_particle_file_name(), 'w'):
+                        with h5py.File(self.get_particle_file_name(), 'w') as particle_file:
                             particle_file.create_group('tracers0/velocity')
         self.run(
                 nb_processes = opt.nb_processes,