diff --git a/colormatrix.go b/colormatrix.go
index 6a78a0bab..554dad97e 100644
--- a/colormatrix.go
+++ b/colormatrix.go
@@ -28,7 +28,7 @@ const ColorMatrixDim = 5
 // Before applying a matrix, a color is un-multiplied, and after applying the matrix,
 // the color is multiplied again.
 type ColorMatrix struct {
-	Elements [ColorMatrixDim - 1][ColorMatrixDim]float64
+	es [ColorMatrixDim - 1][ColorMatrixDim]float64
 }
 
 // ColorMatrixI returns an identity color matrix.
@@ -49,7 +49,7 @@ func (c *ColorMatrix) dim() int {
 
 // Element returns a value of a matrix at (i, j).
 func (c *ColorMatrix) Element(i, j int) float64 {
-	return c.Elements[i][j]
+	return c.es[i][j]
 }
 
 // Concat multiplies a color matrix with the other color matrix.
@@ -65,7 +65,7 @@ func (c *ColorMatrix) IsIdentity() bool {
 }
 
 func (c *ColorMatrix) setElement(i, j int, element float64) {
-	c.Elements[i][j] = element
+	c.es[i][j] = element
 }
 
 // Monochrome returns a color matrix to make an image monochrome.
diff --git a/geometrymatrix.go b/geometrymatrix.go
index b933c0dd2..f478860f6 100644
--- a/geometrymatrix.go
+++ b/geometrymatrix.go
@@ -23,7 +23,7 @@ const GeometryMatrixDim = 3
 
 // A GeometryMatrix represents a matrix to transform geometry when rendering an image.
 type GeometryMatrix struct {
-	Elements [GeometryMatrixDim - 1][GeometryMatrixDim]float64
+	es [GeometryMatrixDim - 1][GeometryMatrixDim]float64
 }
 
 // GeometryMatrixI returns an identity geometry matrix.
@@ -42,7 +42,7 @@ func (g *GeometryMatrix) dim() int {
 
 // Element returns a value of a matrix at (i, j).
 func (g *GeometryMatrix) Element(i, j int) float64 {
-	return g.Elements[i][j]
+	return g.es[i][j]
 }
 
 // Concat multiplies a geometry matrix with the other geometry matrix.
@@ -58,7 +58,7 @@ func (g *GeometryMatrix) IsIdentity() bool {
 }
 
 func (g *GeometryMatrix) setElement(i, j int, element float64) {
-	g.Elements[i][j] = element
+	g.es[i][j] = element
 }
 
 // ScaleGeometry returns a matrix that scales a geometry matrix by (x, y).
diff --git a/geometrymatrix_test.go b/geometrymatrix_test.go
index ca4539f5e..9251430ff 100644
--- a/geometrymatrix_test.go
+++ b/geometrymatrix_test.go
@@ -29,16 +29,8 @@ func TestGeometryIdentity(t *testing.T) {
 }
 
 func TestGeometryConcat(t *testing.T) {
-	matrix1 := GeometryMatrix{}
-	matrix2 := GeometryMatrix{}
-	matrix1.Elements = [2][3]float64{
-		{2, 0, 0},
-		{0, 2, 0},
-	}
-	matrix2.Elements = [2][3]float64{
-		{1, 0, 1},
-		{0, 1, 1},
-	}
+	matrix1 := ScaleGeometry(2, 2)
+	matrix2 := TranslateGeometry(1, 1)
 
 	matrix3 := matrix1
 	matrix3.Concat(matrix2)
@@ -48,7 +40,7 @@ func TestGeometryConcat(t *testing.T) {
 	}
 	for i := 0; i < 2; i++ {
 		for j := 0; j < 3; j++ {
-			got := matrix3.Elements[i][j]
+			got := matrix3.Element(i, j)
 			want := expected[i][j]
 			if want != got {
 				t.Errorf("matrix3.Element(%d, %d) = %f,"+
@@ -66,7 +58,7 @@ func TestGeometryConcat(t *testing.T) {
 	}
 	for i := 0; i < 2; i++ {
 		for j := 0; j < 3; j++ {
-			got := matrix4.Elements[i][j]
+			got := matrix4.Element(i, j)
 			want := expected[i][j]
 			if want != got {
 				t.Errorf("matrix4.Element(%d, %d) = %f, want %f",