diff --git a/src/moments_eq_rhs.F90 b/src/moments_eq_rhs.F90
index 4e5ce055ac020b85a6451039ec47615c1d8d6118..a7d1a71bb0d59329598173c26f8c1af4d2be48e6 100644
--- a/src/moments_eq_rhs.F90
+++ b/src/moments_eq_rhs.F90
@@ -121,7 +121,7 @@ SUBROUTINE moments_eq_rhs_e
               ! Electrostatic background gradients
               - i_ky * K_E * moments_e(ip,ij,ikx,iky,iz,updatetlevel) &
               ! Numerical hyperdiffusion (totally artificial, for stability purpose)
-              - (mu_x*kx**2 + mu_y*ky**2)*moments_e(ip,ij,ikx,iky,iz,updatetlevel) &
+              - (mu_x*kx**4 + mu_y*ky**4)*moments_e(ip,ij,ikx,iky,iz,updatetlevel) &
               ! Collision term
               + TColl_e(ip,ij,ikx,iky,iz)
 
@@ -258,7 +258,7 @@ SUBROUTINE moments_eq_rhs_i
               ! Electrostatic background gradients
               - i_ky * K_E * moments_i(ip,ij,ikx,iky,iz,updatetlevel) &
               ! Numerical hyperdiffusion (totally artificial, for stability purpose)
-              - (mu_x*kx**2 + mu_y*ky**2)*moments_i(ip,ij,ikx,iky,iz,updatetlevel) &
+              - (mu_x*kx**4 + mu_y*ky**4)*moments_i(ip,ij,ikx,iky,iz,updatetlevel) &
               ! Collision term
               + TColl_i(ip,ij,ikx,iky,iz)