diff --git a/MC/bin/o2dpg_sim_workflow.py b/MC/bin/o2dpg_sim_workflow.py
index e793f17f6..9126bd4e9 100755
--- a/MC/bin/o2dpg_sim_workflow.py
+++ b/MC/bin/o2dpg_sim_workflow.py
@@ -615,7 +615,7 @@ def getDPL_global_options(bigshm=False, ccdbbackend=True, runcommand=True):
 # No vertexing for event pool generation; otherwise the vertex comes from CCDB and later from CollContext
 # (Note that the CCDB case covers the kDiamond case, since this is picked up in GRP_TASK)
 vtxmode_precoll = 'kNoVertex' if args.make_evtpool else 'kCCDB'
-vtxmode_sgngen = 'kCollContext'
+vtxmode_sgngen = 'kNoVertex' if args.make_evtpool else 'kCollContext'
 
 # preproduce the collision context / timeframe structure for all timeframes at once
 precollneeds=[GRP_TASK['name']]