diff --git a/README.md b/README.md
index c4dc79a..6779cac 100644
--- a/README.md
+++ b/README.md
@@ -175,6 +175,25 @@ if size.Width != 1000 || size.Height != 500 {
 }
 ```
 
+#### Custom colour space (black & white)
+
+```go
+buffer, err := bimg.Read("image.jpg")
+if err != nil {
+  fmt.Fprintln(os.Stderr, err)
+}
+
+newImage, err := bimg.NewImage(buffer).Colourspace(bimg.INTERPRETATION_B_W)
+if err != nil {
+  fmt.Fprintln(os.Stderr, err)
+}
+  
+colourSpace, _ := bimg.ImageInterpretation(newImage)
+if colourSpace != bimg.INTERPRETATION_B_W {
+  fmt.Fprintln(os.Stderr, "Invalid colour space")
+}
+```
+
 #### Custom options
 
 See [Options](https://godoc.org/github.com/h2non/bimg#Options) struct to discover all the available fields
diff --git a/image_test.go b/image_test.go
index b837dc7..fb20c62 100644
--- a/image_test.go
+++ b/image_test.go
@@ -272,15 +272,25 @@ func TestInterpretation(t *testing.T) {
 	}
 }
 
-func TestImageColourspaceBW(t *testing.T) {
-	buf, err := initImage("test.jpg").Colourspace(INTERPRETATION_B_W)
-	if err != nil {
-		t.Errorf("Cannot process the image: %#v", err)
-	}
-
-	interpretation, err := ImageInterpretation(buf)
-	if interpretation != INTERPRETATION_B_W {
-		t.Errorf("Invalid colourspace")
+func TestImageColourspace(t *testing.T) {
+	tests := []struct {
+		file           string
+		interpretation Interpretation
+	}{
+		{"test.jpg", INTERPRETATION_sRGB},
+		{"test.jpg", INTERPRETATION_B_W},
+	}
+
+	for _, test := range tests {
+		buf, err := initImage(test.file).Colourspace(test.interpretation)
+		if err != nil {
+			t.Errorf("Cannot process the image: %#v", err)
+		}
+
+		interpretation, err := ImageInterpretation(buf)
+		if interpretation != test.interpretation {
+			t.Errorf("Invalid colourspace")
+		}
 	}
 }
 
diff --git a/options.go b/options.go
index 8cf00cf..67af96d 100644
--- a/options.go
+++ b/options.go
@@ -69,6 +69,8 @@ const (
 	INTERPRETATION_RGB16     Interpretation = C.VIPS_INTERPRETATION_RGB16
 	INTERPRETATION_GREY16    Interpretation = C.VIPS_INTERPRETATION_GREY16
 	INTERPRETATION_scRGB     Interpretation = C.VIPS_INTERPRETATION_scRGB
+	INTERPRETATION_LAB       Interpretation = C.VIPS_INTERPRETATION_LAB
+	INTERPRETATION_XYZ       Interpretation = C.VIPS_INTERPRETATION_XYZ
 )
 
 const WATERMARK_FONT = "sans 10"
diff --git a/vips.go b/vips.go
index d9504a7..f41e8de 100644
--- a/vips.go
+++ b/vips.go
@@ -226,10 +226,10 @@ func vipsRead(buf []byte) (*C.struct__VipsImage, ImageType, error) {
 
 func vipsColourspaceIsSupportedBuffer(buf []byte) (bool, error) {
 	image, _, err := vipsRead(buf)
-	defer C.g_object_unref(C.gpointer(image))
 	if err != nil {
 		return false, err
 	}
+	C.g_object_unref(C.gpointer(image))
 	return vipsColourspaceIsSupported(image), nil
 }
 
@@ -239,10 +239,10 @@ func vipsColourspaceIsSupported(image *C.struct__VipsImage) bool {
 
 func vipsInterpretationBuffer(buf []byte) (Interpretation, error) {
 	image, _, err := vipsRead(buf)
-	defer C.g_object_unref(C.gpointer(image))
 	if err != nil {
-		return Interpretation(-1), err
+		return INTERPRETATION_ERROR, err
 	}
+	C.g_object_unref(C.gpointer(image))
 	return vipsInterpretation(image), nil
 }
 
@@ -266,10 +266,10 @@ func vipsPreSave(image *C.struct__VipsImage, o *vipsSaveOptions) (*C.struct__Vip
 	var outImage *C.struct__VipsImage
 	if vipsColourspaceIsSupported(image) {
 		err := int(C.vips_colourspace_bridge(image, &outImage, interpretation))
-		C.g_object_unref(C.gpointer(image))
 		if err != 0 {
 			return nil, catchVipsError()
 		}
+		C.g_object_unref(C.gpointer(image))
 		image = outImage
 	}