diff --git a/src/fmpz_mat/minpoly_modular.c b/src/fmpz_mat/minpoly_modular.c
index 28a69aaa45..fdbd6bebb5 100644
--- a/src/fmpz_mat/minpoly_modular.c
+++ b/src/fmpz_mat/minpoly_modular.c
@@ -42,7 +42,7 @@ static slong _fmpz_mat_minpoly_small(fmpz * rop, const fmpz_mat_t op)
 static void _fmpz_mat_bound_ovals_of_cassini(fmpz_t b, const fmpz_mat_t op)
 {
    slong n = op->r, i, j;
-   fmpz * v1;
+   fmpz * v1, * v2;
    fmpz_t t, q, r1, r2;
 
    fmpz_init(t);
@@ -51,6 +51,7 @@ static void _fmpz_mat_bound_ovals_of_cassini(fmpz_t b, const fmpz_mat_t op)
    fmpz_init(r2);
 
    v1 = _fmpz_vec_init(n);
+   v2 = _fmpz_vec_init(n);
 
    /* |A| [1,1,...,1]^T */
    for (i = 0; i < n; i++)
@@ -63,13 +64,27 @@ static void _fmpz_mat_bound_ovals_of_cassini(fmpz_t b, const fmpz_mat_t op)
             fmpz_sub(v1 + i, v1 + i, fmpz_mat_entry(op, i, j));
       }
    }
+   /* |A|^t * |A| * [1,1,...,1]^T */
+   for (i = 0; i < n; i++)
+   {
+      for (j = 0; j < n; j++)
+      {
+         if (fmpz_sgn(fmpz_mat_entry(op, j, i)) >= 0)
+            fmpz_addmul(v2 + i, v1 + j, fmpz_mat_entry(op, j, i));
+         else
+            fmpz_submul(v2 + i, v1 + j, fmpz_mat_entry(op, j, i));
+      }
+   }
+
+   _fmpz_vec_clear(v1, n);
+   v1 = v2;
 
    for (i = 0; i < n; i++)
    {
       fmpz_zero(t);
-
       /* q_i */
-      fmpz_abs(t, fmpz_mat_entry(op, i, i));
+      for (j = 1; j < n; j++)
+         fmpz_addmul(t, fmpz_mat_entry(op, i, j), fmpz_mat_entry(op, i, j));
 
       if (fmpz_cmp(t, q) > 0)
          fmpz_set(q, t);
diff --git a/src/fmpz_mat/test/t-minpoly.c b/src/fmpz_mat/test/t-minpoly.c
index f48dcaa4b9..457f8786c6 100644
--- a/src/fmpz_mat/test/t-minpoly.c
+++ b/src/fmpz_mat/test/t-minpoly.c
@@ -52,7 +52,7 @@ TEST_FUNCTION_START(fmpz_mat_minpoly, state)
         fmpz_poly_init(r);
 
         if (n_randint(state, 50) == 0)
-            fmpz_mat_randtest(A, state, 1000);
+            fmpz_mat_randtest(A, state, 10000);
         else
             fmpz_mat_randtest(A, state, 10);