diff --git a/base/netcmp.c b/base/netcmp.c
index 539a191..8d8efbc 100644
--- a/base/netcmp.c
+++ b/base/netcmp.c
@@ -6952,7 +6952,8 @@ int EquivalenceClasses(char *name1, int file1, char *name2, int file2)
       /* conflicting names exist, then alter the classhash to make it	*/
       /* unique.  In the case of duplicate cells, don't do this.	*/
 
-      if (!(tp->flags & CELL_DUPLICATE) && !(tp2->flags & CELL_DUPLICATE)) {
+      if (!(tp->flags & CELL_DUPLICATE) && !(tp2->flags & CELL_DUPLICATE) &&
+			!(*matchfunc)(name1, name2)) {
 	 tpx = LookupCellFile(name1, file2);
 	 if (tpx != NULL) need_new_seed = 1;
 	 tpx = LookupCellFile(name2, file1);