diff --git a/src/lammps.cpp b/src/lammps.cpp
index 21335065f4..fcdfecf30a 100644
--- a/src/lammps.cpp
+++ b/src/lammps.cpp
@@ -309,6 +309,7 @@ LAMMPS::LAMMPS(int narg, char **arg, MPI_Comm communicator)
       iarg += 3;
       while (iarg < narg && arg[iarg][0] != '-') iarg++;
 
+    } else error->universe_all(FLERR,"Invalid command-line argument");
   }
 
   // if no partition command-line switch, universe is one world with all procs