diff --git a/MC/bin/o2dpg_sim_workflow.py b/MC/bin/o2dpg_sim_workflow.py
index f7eada9e0..d429af3a3 100755
--- a/MC/bin/o2dpg_sim_workflow.py
+++ b/MC/bin/o2dpg_sim_workflow.py
@@ -25,6 +25,7 @@
 import random
 import json
 import itertools
+import math
 import requests, re
 pandas_available = True
 try:
@@ -119,7 +120,7 @@
 parser.add_argument('--combine-tpc-clusterization', action='store_true', help=argparse.SUPPRESS) #<--- useful for small productions (pp, low interaction rate, small number of events)
 parser.add_argument('--first-orbit', default=0, type=int, help=argparse.SUPPRESS)  # to set the first orbit number of the run for HBFUtils (only used when anchoring)
                                                             # (consider doing this rather in O2 digitization code directly)
-parser.add_argument('--orbits-early', default=0, type=int, help=argparse.SUPPRESS) # number of orbits to start simulating earlier
+parser.add_argument('--orbits-early', default=0, type=float, help=argparse.SUPPRESS) # number of orbits to start simulating earlier
                                                                                    # to reduce start of timeframe effects in MC --> affects collision context
 parser.add_argument('--sor', default=-1, type=int, help=argparse.SUPPRESS) # may pass start of run with this (otherwise it is autodetermined from run number)
 parser.add_argument('--run-anchored', action='store_true', help=argparse.SUPPRESS)
@@ -627,7 +628,7 @@ def getDPL_global_options(bigshm=False, ccdbbackend=True):
    PreCollContextTask=createTask(name='precollcontext_' + str(tf), needs=precollneeds, tf=tf, cwd=timeframeworkdir, cpu='1')
    PreCollContextTask['cmd']='${O2_ROOT}/bin/o2-steer-colcontexttool -i ' + signalprefix + ',' + str(INTRATE) + ',' + str(args.ns) + ':' + str(args.ns) \
                               + ' --show-context ' + ' --timeframeID ' + str(tf-1 + int(args.production_offset)*NTIMEFRAMES)                            \
-                              + ' --orbitsPerTF ' + str(orbitsPerTF) + ' --orbits ' + str(orbitsPerTF + args.orbits_early)                                                  \
+                              + ' --orbitsPerTF ' + str(orbitsPerTF) + ' --orbits ' + str(orbitsPerTF + math.ceil(args.orbits_early))                                                  \
                               + ' --seed ' + str(TFSEED) + ' --noEmptyTF --first-orbit ' + str(args.first_orbit - args.orbits_early)
    PreCollContextTask['cmd'] += ' --bcPatternFile ccdb'  # <--- the object should have been set in (local) CCDB
    if includeQED: