diff --git a/src/rt/RcontribSimulManager.cpp b/src/rt/RcontribSimulManager.cpp
index c09c978e..5cc5daed 100644
--- a/src/rt/RcontribSimulManager.cpp
+++ b/src/rt/RcontribSimulManager.cpp
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: RcontribSimulManager.cpp,v 2.4 2024/11/01 16:17:33 greg Exp $";
+static const char RCSid[] = "$Id: RcontribSimulManager.cpp,v 2.5 2024/11/01 23:05:01 greg Exp $";
 #endif
 /*
  *  RcontribSimulManager.cpp
@@ -148,7 +148,7 @@ RcontribSimulManager::RctCall(RAY *r, void *cd)
 
 	int			bi = 0;	// get bin index
 	if (mp->binv) {
-		worldfunc(RCCONTEXT, r);	// compute bin #
+		worldfunc(RCCONTEXT, r);
 		set_eparams(mp->params);
 		double		bval = evalue(mp->binv);
 		if (bval <= -.5)
@@ -324,6 +324,10 @@ RcontribSimulManager::PrepOutput()
 		error(INTERNAL, "PrepOutput() called before octree & modifiers assigned");
 		return -1;
 	}
+	if (!cdsF) {
+		error(INTERNAL, "missing RdataShare constructor call (*cdsF)");
+		return -1;
+	}
 	if (lu_doall(&modLUT, checkModExists, NULL) < 0)
 		return -1;
 
diff --git a/src/rt/RcontribSimulManager.h b/src/rt/RcontribSimulManager.h
index 9c030807..6a9a54a8 100644
--- a/src/rt/RcontribSimulManager.h
+++ b/src/rt/RcontribSimulManager.h
@@ -1,4 +1,4 @@
-/* RCSid $Id: RcontribSimulManager.h,v 2.3 2024/10/30 01:38:21 greg Exp $ */
+/* RCSid $Id: RcontribSimulManager.h,v 2.4 2024/11/01 23:05:01 greg Exp $ */
 /*
  *  RcontribSimulManager.h
  *
@@ -279,7 +279,7 @@ class RcontribSimulManager : protected RtraceSimulManager {
 	int			PrepOutput();
 				/// Are we ready to compute some records?
 	bool			Ready() const {
-					return rowsDone.Length();
+					return (rowsDone.Length() > 0) & (accum > 0);
 				}
 				/// Set number of computation threads (0 => #cores)
 	int			SetThreadCount(int nt = 0);