diff --git a/src/cost.c b/src/cost.c
index 7e78a34..38e6adf 100644
--- a/src/cost.c
+++ b/src/cost.c
@@ -35,6 +35,7 @@ attackCost (const System sys)
   cost += get_semitrace_length ();
   cost += 8 * selfInitiators (sys);
   cost += 4 * selfResponders (sys);
+  cost += 2 * countInitiators (sys);
 
   return cost;
 }
diff --git a/src/system.c b/src/system.c
index dedf3f7..99fc117 100644
--- a/src/system.c
+++ b/src/system.c
@@ -1399,6 +1399,24 @@ eventRoledef (const System sys, const int run, const int ev)
   return roledef_shift (sys->runs[run].start, ev);
 }
 
+//! count the number of initiators
+int
+countInitiators (const System sys)
+{
+  int run;
+  int count;
+
+  count = 0;
+  for (run = 0; run < sys->maxruns; run++)
+    {
+      if (sys->runs[run].role->initiator)
+	{
+	  count++;
+	}
+    }
+  return count;
+}
+
 //! determine whether a run talks to itself
 int
 selfSession (const System sys, const int run)
diff --git a/src/system.h b/src/system.h
index 968435f..1288711 100644
--- a/src/system.h
+++ b/src/system.h
@@ -201,6 +201,7 @@ int iterateLocalToOther (const System sys, const int myrun,
 			 int (*callback) (Term t));
 int firstOccurrence (const System sys, const int r, Term t, int evtype);
 Roledef eventRoledef (const System sys, const int run, const int ev);
+int countInitiators (const System sys);
 int selfResponder (const System sys, const int run);
 int selfResponders (const System sys);
 int selfInitiator (const System sys, const int run);