diff --git a/dynamics/spam/Dycore.h b/dynamics/spam/Dycore.h
index 5091de60..acd272b8 100644
--- a/dynamics/spam/Dycore.h
+++ b/dynamics/spam/Dycore.h
@@ -231,10 +231,13 @@ class Dycore {
   }
 
   void update_dt(pam::PamCoupler &coupler) {
-    if (params.tstype != "si") {
-      params.dt_crm_phys = coupler.get_option<real>("crm_dt");
-      params.dtcrm = params.dt_crm_phys / params.crm_per_phys;
+    if (params.tstype=="si") {
+      serial_print("ERROR - update_dt: time step cannot be updated in SI mode", par.masterproc);
+      exit(-1);
     }
+    params.dt_crm_phys = coupler.get_option<real>("crm_dt");
+    params.dtcrm = params.dt_crm_phys / params.crm_per_phys;
+    
   }
 
   // Given the model data and CFL value, compute the maximum stable time step