diff --git a/src/hydro/AnarchyDU/hydro_iact.h b/src/hydro/AnarchyDU/hydro_iact.h
index 19489f7460753b15961603e68c22c039f6de27d3..09ecde01d44cfef1c0edbfe0d3f1aa909d553a95 100644
--- a/src/hydro/AnarchyDU/hydro_iact.h
+++ b/src/hydro/AnarchyDU/hydro_iact.h
@@ -428,6 +428,12 @@ __attribute__((always_inline)) INLINE static void runner_iact_force(
   /* Get the time derivative for h. */
   pi->force.h_dt -= mj * dvdr * r_inv / rhoj * wi_dr;
   pj->force.h_dt -= mi * dvdr * r_inv / rhoi * wj_dr;
+
+  /* Update if we need to; this should be guaranteed by the gradient loop but
+   * due to some possible synchronisation problems this is here as a _quick
+   * fix_. Added: 14th August 2019. To be removed by 1st Jan 2020. (JB) */
+  pi->viscosity.v_sig = max(pi->viscosity.v_sig, v_sig);
+  pj->viscosity.v_sig = max(pj->viscosity.v_sig, v_sig);
 }
 
 /**
@@ -547,6 +553,11 @@ __attribute__((always_inline)) INLINE static void runner_iact_nonsym_force(
 
   /* Get the time derivative for h. */
   pi->force.h_dt -= mj * dvdr * r_inv / rhoj * wi_dr;
+
+  /* Update if we need to; this should be guaranteed by the gradient loop but
+   * due to some possible synchronisation problems this is here as a _quick
+   * fix_. Added: 14th August 2019. To be removed by 1st Jan 2020. (JB) */
+  pi->viscosity.v_sig = max(pi->viscosity.v_sig, v_sig);
 }
 
 /**