diff --git a/source/gemc.cc b/source/gemc.cc
index b22a263..28d9a86 100644
--- a/source/gemc.cc
+++ b/source/gemc.cc
@@ -414,4 +414,5 @@ int main( int argc, char **argv )
 
 // introducing OPTICALPHOTONPID here to be semi-transparent to G4 changes
 // this pid changed from 0 to -22 with geant4 10.7
-int MHit::OPTICALPHOTONPID = -22;
+// int MHit::OPTICALPHOTONPID = -22;
+int MHit::OPTICALPHOTONPID = 0;