Index: parmchk.c
===================================================================
RCS file: /thr/gamow/cvsroot/amber8/src/antechamber/parmchk.c,v
retrieving revision 1.24
diff -c -r1.24 parmchk.c
*** parmchk.c	2004/02/02 21:46:47	1.24
--- parmchk.c	2005/12/03 04:19:17
***************
*** 255,260 ****
--- 255,262 ----
  			improper[impropernum].atid2 = atom[i].con[0];
  			improper[impropernum].atid3 = atom[i].con[1];
  			improper[impropernum].atid4 = atom[i].con[2];
+ 			if(atom[i].con[0] <0 || atom[i].con[1] <0 || atom[i].con[2] <0)
+ 				continue;
  			impropernum++;
  		}
  }