diff --git a/examples/main.c b/examples/main.c
index b897be3d79242b422b3bd5a2b4a4aac2519faed6..e075151c62ccba8d83b5bbca0f59be1ea3eedf35 100644
--- a/examples/main.c
+++ b/examples/main.c
@@ -193,8 +193,8 @@ int main(int argc, char *argv[]) {
                   "Run with self-gravity.", NULL, 0, 0),
       OPT_BOOLEAN('M', "multipole-reconstruction", &with_mpole_reconstruction,
                   "Reconstruct the multipoles every time-step.", NULL, 0, 0),
-      OPT_BOOLEAN('s', "hydro", &with_hydro, "Run with hydrodynamics.",
-                  NULL, 0, 0),
+      OPT_BOOLEAN('s', "hydro", &with_hydro, "Run with hydrodynamics.", NULL, 0,
+                  0),
       OPT_BOOLEAN('S', "stars", &with_stars, "Run with stars", NULL, 0, 0),
       OPT_BOOLEAN('x', "velociraptor", &with_structure_finding,
                   "Run with structure finding", NULL, 0, 0),