diff --git a/src/glpapi06.c b/src/glpapi06.c
index 4a5267c..f23fb25 100644
--- a/src/glpapi06.c
+++ b/src/glpapi06.c
@@ -245,7 +245,10 @@ static int solve_lp(glp_prob *P, const glp_smcp *parm)
          if (ret != 0) goto done;
       }
       if (parm->meth == GLP_PRIMAL)
-         ret = spx_primal(P, parm);
+      {  ret = spx_primal(P, parm);
+         if (ret == -1 && P->valid)
+            ret = spx_dual(P, parm);
+      }
       else if (parm->meth == GLP_DUALP)
       {  ret = spx_dual(P, parm);
          if (ret == GLP_EFAIL && P->valid)
diff --git a/src/simplex/spxprim.c b/src/simplex/spxprim.c
index 3f09b6c..ad29b4f 100644
--- a/src/simplex/spxprim.c
+++ b/src/simplex/spxprim.c
@@ -1040,6 +1040,12 @@ loop: /* main loop starts here */
                xprintf("Perturbation removed at iteration %d\n",
                   csa->it_cnt);
 #endif
+            if (check_feas(csa, 2, tol_bnd, tol_bnd1))
+            {  if (msg_lev >= GLP_MSG_ALL)
+                  xprintf("Switching to dual\n");
+               ret = -1;
+               goto fini;
+            }
          }
 #endif
          if (csa->beta_st != 1)