diff --git a/src/simplex/spydual.c b/src/simplex/spydual.c
index e41baf2..42f5fc9 100644
--- a/src/simplex/spydual.c
+++ b/src/simplex/spydual.c
@@ -1288,7 +1288,7 @@ loop: /* main loop starts here */
             }
          }
          /* make sure that current basic solution is dual feasible */
-#if 0 /* 29/III-2016 */
+#if !PERTURB /* 29/III-2016 */
          j = check_feas(csa, tol_dj, tol_dj1, 0);
 #else
          if (perturb)