diff --git a/diff/fd/hessian_test.go b/diff/fd/hessian_test.go
index af1b13905..04c21f8d2 100644
--- a/diff/fd/hessian_test.go
+++ b/diff/fd/hessian_test.go
@@ -63,7 +63,7 @@ func TestHessian(t *testing.T) {
 					2, 5, -3,
 					1, -3, 6,
 				}),
-				b: mat.NewVector(3, []float64{3, -2, -1}),
+				b: mat.NewVecDense(3, []float64{3, -2, -1}),
 				c: 5,
 			},
 			x:   []float64{-1.6, -3, 2},
diff --git a/diff/fd/simplefunctions_test.go b/diff/fd/simplefunctions_test.go
index 2a7c77a65..1c1dd42e9 100644
--- a/diff/fd/simplefunctions_test.go
+++ b/diff/fd/simplefunctions_test.go
@@ -57,20 +57,20 @@ func (l LinearFunc) Hess(dst mat.MutableSymmetric, x []float64) {
 // QuadFunc is a quadratic function returning 0.5*x'*a*x + b*x + c.
 type QuadFunc struct {
 	a *mat.SymDense
-	b *mat.Vector
+	b *mat.VecDense
 	c float64
 }
 
 func (q QuadFunc) Func(x []float64) float64 {
-	v := mat.NewVector(len(x), x)
-	var tmp mat.Vector
+	v := mat.NewVecDense(len(x), x)
+	var tmp mat.VecDense
 	tmp.MulVec(q.a, v)
 	return 0.5*mat.Dot(&tmp, v) + mat.Dot(q.b, v) + q.c
 }
 
 func (q QuadFunc) Grad(grad, x []float64) {
-	var tmp mat.Vector
-	v := mat.NewVector(len(x), x)
+	var tmp mat.VecDense
+	v := mat.NewVecDense(len(x), x)
 	tmp.MulVec(q.a, v)
 	for i := range grad {
 		grad[i] = tmp.At(i, 0) + q.b.At(i, 0)