diff --git a/algo/detectors/rich/Unpack.h b/algo/detectors/rich/Unpack.h
index 7786e7b3f39983416e96ddb2b85566acaa41b812..b741a56f697f93f8995fa5b505eeca4d7f1ae937 100644
--- a/algo/detectors/rich/Unpack.h
+++ b/algo/detectors/rich/Unpack.h
@@ -133,6 +133,13 @@ namespace cbm::algo::rich
       u64 cbmTimePacket = 0;
       u64 refTime       = 0;
 
+      // FIXME: Magic number, should be named.
+      //
+      // Comment from RICH expert (Martin Beyer):
+      //  > This number will also be valid for the Cbm Rich, 1 Rich backplane contains max. 12 DiRICHes.
+      //  > For the Cbm Rich the number of backplanes will be scaled
+      //  > up. Nevertheless it is very likely that fewer DiRiches(maybe not constant)
+      //  > per backplane are used in the day1 setup.
       double prevLastCh0ReTime[13];  // 12 DiRICHes chnl0 + 1 CTS chnl0
       double mbsCorr = 0.;