Warning in Grompp command

GROMACS version:
GROMACS modification: Yes/No
Here post your question
while running the following command
gmx grompp -f em.mdp -c 1_ions.gro -p topol.top -o em.tpr
i am getting the following issue
WARNING 1 [file topol.top, line 104856]:
You are using Ewald electrostatics in a system with net charge. This can
lead to severe artifacts, such as ions moving into regions with low
dielectric, due to the uniform background charge. We suggest to
neutralize your system with counter ions, possibly in combination with a
physiological salt concentration.