diff --git a/mat/vector.go b/mat/vector.go
index 8191312b..f65bbf1e 100644
--- a/mat/vector.go
+++ b/mat/vector.go
@@ -226,7 +226,11 @@ func (v *VecDense) CopyVec(a Vector) int {
 		return n
 	}
 	if r, ok := a.(RawVectorer); ok {
-		blas64.Copy(r.RawVector(), v.mat)
+		src := r.RawVector()
+		src.N = n
+		dst := v.mat
+		dst.N = n
+		blas64.Copy(src, dst)
 		return n
 	}
 	for i := 0; i < n; i++ {
diff --git a/mat/vector_test.go b/mat/vector_test.go
index b721db5b..28a67505 100644
--- a/mat/vector_test.go
+++ b/mat/vector_test.go
@@ -310,6 +310,32 @@ func TestVecDenseScale(t *testing.T) {
 	}
 }
 
+func TestCopyVec(t *testing.T) {
+	for i, test := range []struct {
+		src   *VecDense
+		dst   *VecDense
+		want  *VecDense
+		wantN int
+	}{
+		{src: NewVecDense(1, nil), dst: NewVecDense(1, nil), want: NewVecDense(1, nil), wantN: 1},
+		{src: NewVecDense(3, []float64{1, 2, 3}), dst: NewVecDense(2, []float64{-1, -2}), want: NewVecDense(2, []float64{1, 2}), wantN: 2},
+		{src: NewVecDense(2, []float64{1, 2}), dst: NewVecDense(3, []float64{-1, -2, -3}), want: NewVecDense(3, []float64{1, 2, -3}), wantN: 2},
+	} {
+		got := test.dst
+		var n int
+		panicked, message := panics(func() { n = got.CopyVec(test.src) })
+		if panicked {
+			t.Errorf("unexpected panic during vector copy for test %d: %s", i, message)
+		}
+		if !Equal(got, test.want) {
+			t.Errorf("test %d: unexpected result CopyVec:\ngot: %v\nwant:%v", i, got, test.want)
+		}
+		if n != test.wantN {
+			t.Errorf("test %d: unexpected result number of elements copied: got:%d want:%d", i, n, test.wantN)
+		}
+	}
+}
+
 func TestVecDenseAddScaled(t *testing.T) {
 	for _, alpha := range []float64{0, 1, -1, 2.3, -2.3} {
 		method := func(receiver, a, b Matrix) {