diff --git a/src/collision/collision_regime.f90 b/src/collision/collision_regime.f90
index ad06f9c5b..7480c6a0d 100644
--- a/src/collision/collision_regime.f90
+++ b/src/collision/collision_regime.f90
@@ -288,7 +288,9 @@ subroutine collision_regime_LS12_SI(Mcb, m1, m2, rad1, rad2, rh1, rh2, vb1, vb2,
       Msmall = Mtot - Mbig
       if (Msmall < min_mfrag) then
          regime = COLLRESOLVE_REGIME_MERGE
+         Mbig = Mtot
          Mslr = 0.0_DP
+         Mslr_hitandrun = 0.0_DP
       else
          Mslr_hitandrun = max(calc_Qrd_rev(Msmall, Mbig, Mint, den1, den2, Vimp, c_star), min_mfrag)
          if (regime == COLLRESOLVE_REGIME_HIT_AND_RUN ) then