diff --git a/BEAMS3D/Sources/beams3d_physics_mod.f90 b/BEAMS3D/Sources/beams3d_physics_mod.f90
index 65605954..81247d56 100644
--- a/BEAMS3D/Sources/beams3d_physics_mod.f90
+++ b/BEAMS3D/Sources/beams3d_physics_mod.f90
@@ -386,8 +386,8 @@ SUBROUTINE beams3d_physics_gc(t, q)
             !-----------------------------------------------------------
             dve   = speed*tau_spit_inv*(1-2*te_temp*inv_mymass*e_charge/speed**2.0)
             dvi   = vc3_tauinv/(speed*speed)*(1+ti_temp*inv_mymass*e_charge/speed**2.0)
-            reduction = dve + dvi
-            newspeed = speed - reduction*dt+sigma*zeta
+            reduction = (dve + dvi)*dt+sigma*zeta
+            newspeed = speed - reduction
             dve=dve+ddve
             dvi=dvi+ddvi
             vfrac = newspeed/speed