--- src/AlgebraicCore/TmpFactorDir/linalg/Qsolve.c.orig	2008-12-16 14:05:53.000000000 -0700

+++ src/AlgebraicCore/TmpFactorDir/linalg/Qsolve.c	2018-06-14 14:56:08.127685643 -0600

@@ -321,9 +321,8 @@ int Qsolve(Qmat soln, Qmat M, Qmat rhs)

   for (i=0; i < M->ncols; i++) shape[i] = 0;

   step_size = 3;

   count_down = 3;

-  while(1)

+  for (p = NextPrime(PS); p != 0; p = NextPrime(PS))

   {

-    p = NextPrime(PS);

     FFp = FFctor(p);

     FFselect(FFp);

     /* Skip unsuitable primes */

@@ -374,8 +373,15 @@ int Qsolve(Qmat soln, Qmat M, Qmat rhs)

   FFmat_dtor(solnp);

   /* Compute the rank */

-  r = 0;

-  for (i=0; i < M->ncols; i++) r += shape[i];

+  if (p == 0)

+  {

+    r = -1;

+  }

+  else

+  {

+    r = 0;

+    for (i=0; i < M->ncols; i++) r += shape[i];

+  }

   FREE(shape);

   return r;