diff --git a/run/CMakeLists.txt b/run/CMakeLists.txt
index f21ecafb0528a..662716901ed0a 100644
--- a/run/CMakeLists.txt
+++ b/run/CMakeLists.txt
@@ -193,6 +193,8 @@ o2_add_test_command(NAME o2sim_G4
                                       2
                                       --skipModules
                                       MFT ZDC
+                                      --seed
+                                      15946057944514955802
                                       --configKeyValues
                                       "align-geom.mDetectors=none"
                     ENVIRONMENT "${SIMENV}"
@@ -255,6 +257,8 @@ o2_add_test_command(NAME o2sim_G3
                                       pythia8pp
                                       --chunkSize
                                       10
+                                      --seed
+                                      15946057944514955802
                                       --configKeyValues
                                       "align-geom.mDetectors=none"
                     LABELS g3 sim long
diff --git a/run/checkStack.cxx b/run/checkStack.cxx
index 98f2669c9f97e..36a9da7a62c13 100644
--- a/run/checkStack.cxx
+++ b/run/checkStack.cxx
@@ -144,7 +144,7 @@ int main(int argc, char** argv)
       for (auto& trackID : trackidsinTPC) {
         auto tpc_trackrefs = mcreader.getTrackRefs(eventID, trackID);
         LOG(debug) << " Track " << trackID << " has " << tpc_trackrefs.size() << " TrackRefs";
-        // assert(tpc_trackrefs.size() > 0);
+        assert(tpc_trackrefs.size() > 0);
         for (auto& ref : tpc_trackrefs) {
           assert(ref.getTrackID() == trackID);
         }