diff --git a/src/MC/fix_gcmc.cpp b/src/MC/fix_gcmc.cpp
index cdf28a7de5a81726dfbb1bd932ada90e99548391..d65ea8bda02befbdfc606373b83db37476c3c13c 100644
--- a/src/MC/fix_gcmc.cpp
+++ b/src/MC/fix_gcmc.cpp
@@ -510,7 +510,7 @@ void FixGCMC::init()
     sprintf(group_arg[0],"FixGCMC:rotation_gas_atoms:%s",id);
     group_arg[1] = (char *) "molecule";
     char digits[12];
-    sprintf(digits,"%d",ngcmc_type);
+    sprintf(digits,"%d",-1);
     group_arg[2] = digits;
     group->assign(3,group_arg);
     molecule_group = group->find(group_arg[0]);