diff --git a/DataFormats/Detectors/ITSMFT/ITS/include/DataFormatsITS/TrackITS.h b/DataFormats/Detectors/ITSMFT/ITS/include/DataFormatsITS/TrackITS.h
index a2b774d75071e..20d16e3c43097 100644
--- a/DataFormats/Detectors/ITSMFT/ITS/include/DataFormatsITS/TrackITS.h
+++ b/DataFormats/Detectors/ITSMFT/ITS/include/DataFormatsITS/TrackITS.h
@@ -106,7 +106,7 @@ class TrackITSExt : public TrackITS
   ///< heavy version of TrackITS, with clusters embedded
  public:
   static constexpr int MaxClusters = 16; /// Prepare for overlaps and new detector configurations
-  using TrackITS::TrackITS; // inherit base constructors
+  using TrackITS::TrackITS;              // inherit base constructors
 
   TrackITSExt(o2::track::TrackParCov&& parCov, short ncl, float chi2,
               o2::track::TrackParCov&& outer, std::array<int, MaxClusters> cls)
@@ -128,6 +128,9 @@ class TrackITSExt : public TrackITS
   {
     if (newCluster) {
       getClusterRefs().setEntries(getNumberOfClusters() + 1);
+      uint16_t pattern = getPattern();
+      pattern |= 0x1 << layer;
+      setPattern(pattern);
     }
     mIndex[layer] = idx;
   }
diff --git a/Detectors/ITSMFT/ITS/tracking/src/Tracker.cxx b/Detectors/ITSMFT/ITS/tracking/src/Tracker.cxx
index 367e2163472be..0494167213135 100644
--- a/Detectors/ITSMFT/ITS/tracking/src/Tracker.cxx
+++ b/Detectors/ITSMFT/ITS/tracking/src/Tracker.cxx
@@ -583,9 +583,22 @@ void Tracker::computeTracksMClabels(const ROframe& event)
           count = 1;
         }
       }
-      track.setExternalClusterIndex(iCluster, event.getClusterExternalIndex(iCluster, index));
     }
 
+    uint8_t patt{0};
+    // set fake clusters pattern
+    for (int ic{TrackITSExt::MaxClusters}; ic--;) {
+      auto clid = track.getClusterIndex(ic);
+      if (clid != constants::its::UnusedIndex) {
+        const MCCompLabel& currentLabel = event.getClusterLabels(ic, clid);
+        if (currentLabel != maxOccurrencesValue) {
+          patt |= 0x1 << ic; // if cluster label is different from main label
+        }
+        track.setExternalClusterIndex(ic, event.getClusterExternalIndex(ic, clid));
+      }
+    }
+
+    track.setUserField(patt);
     if (isFakeTrack) {
       maxOccurrencesValue.setFakeFlag();
     }