diff --git a/src/simplex/spxprim.c b/src/simplex/spxprim.c
index 4a5e7aa..1f4aac8 100644
--- a/src/simplex/spxprim.c
+++ b/src/simplex/spxprim.c
@@ -963,7 +963,13 @@ loop: /* main loop starts here */
       else
          spx_nt_prod(lp, nt, trow, 1, -1.0, rho);
       /* FIXME: tcol[p] and trow[q] should be close to each other */
-      xassert(trow[csa->q] != 0.0);
+      if (trow[csa->q] == 0.0)
+      {  if (msg_lev >= GLP_MSG_ERR)
+            xprintf("Error: trow[q] == 0.0\n");
+         csa->p_stat = csa->d_stat = GLP_UNDEF;
+         ret = GLP_EFAIL;
+         goto fini;
+      }
       /* update reduced costs of non-basic variables for adjacent
        * basis */
       if (spx_update_d(lp, d, csa->p, csa->q, trow, tcol) <= 1e-9)
diff --git a/src/simplex/spydual.c b/src/simplex/spydual.c
index d33ebb1..c8350d2 100644
--- a/src/simplex/spydual.c
+++ b/src/simplex/spydual.c
@@ -1632,7 +1632,13 @@ loop: /* main loop starts here */
       t_pivcol += timer() - t_start;
 #endif
       /* FIXME: tcol[p] and trow[q] should be close to each other */
-      xassert(csa->tcol.vec[csa->p] != 0.0);
+      if (csa->tcol.vec[csa->p] == 0.0)
+      {  if (msg_lev >= GLP_MSG_ERR)
+            xprintf("Error: tcol[p] == 0.0\n");
+         csa->p_stat = csa->d_stat = GLP_UNDEF;
+         ret = GLP_EFAIL;
+         goto fini;
+      }
       /* update values of basic variables for adjacent basis */
       k = head[csa->p]; /* x[k] = xB[p] */
       p_flag = (l[k] != u[k] && beta[csa->p] > u[k]);