diff --git a/tests/test_vorticity_equation.py b/tests/test_vorticity_equation.py
index f4305b551e7d3d34baf46950a5f9cf7d89e81e3c..dfaccb8bf352bdd252e5edf29f6e7d711689f7dc 100644
--- a/tests/test_vorticity_equation.py
+++ b/tests/test_vorticity_equation.py
@@ -305,7 +305,7 @@ def main():
                  '--np', '4',
                  '--ntpp', '1',
                  '--niter_todo', '{0}'.format(niterations),
-                 '--niter_out', '{0}'.format(niterations},
+                 '--niter_out', '{0}'.format(niterations),
                  '--niter_stat', '1',
                  '--checkpoints_per_file', '{0}'.format(3),
                  '--nparticles', '{0}'.format(nparticles),