diff --git a/schema/config_test.go b/schema/config_test.go
index 27c14875c..98c760adf 100644
--- a/schema/config_test.go
+++ b/schema/config_test.go
@@ -156,7 +156,7 @@ func TestConfig(t *testing.T) {
 		},
 	} {
 		r := strings.NewReader(tt.config)
-		err := schema.MediaTypeImageConfig.Validate(r)
+		err := schema.MediaTypeImageConfig.Validate(r, false)
 
 		if got := err != nil; tt.fail != got {
 			t.Errorf("test %d: expected validation failure %t but got %t, err %v", i, tt.fail, got, err)
diff --git a/schema/manifest_backwards_compatibility_test.go b/schema/manifest_backwards_compatibility_test.go
index 4bd055cbf..80b2a73ec 100644
--- a/schema/manifest_backwards_compatibility_test.go
+++ b/schema/manifest_backwards_compatibility_test.go
@@ -118,7 +118,7 @@ func TestBackwardsCompatibilityManifestList(t *testing.T) {
 
 		manifest := convertFormats(tt.manifest)
 		r := strings.NewReader(manifest)
-		err := schema.MediaTypeManifestList.Validate(r)
+		err := schema.MediaTypeManifestList.Validate(r, false)
 
 		if got := err != nil; tt.fail != got {
 			t.Errorf("test %d: expected validation failure %t but got %t, err %v", i, tt.fail, got, err)
@@ -181,7 +181,7 @@ func TestBackwardsCompatibilityManifest(t *testing.T) {
 
 		manifest := convertFormats(tt.manifest)
 		r := strings.NewReader(manifest)
-		err := schema.MediaTypeManifest.Validate(r)
+		err := schema.MediaTypeManifest.Validate(r, false)
 
 		if got := err != nil; tt.fail != got {
 			t.Errorf("test %d: expected validation failure %t but got %t, err %v", i, tt.fail, got, err)
@@ -221,7 +221,7 @@ func TestBackwardsCompatibilityConfig(t *testing.T) {
 
 		config := convertFormats(tt.config)
 		r := strings.NewReader(config)
-		err := schema.MediaTypeImageConfig.Validate(r)
+		err := schema.MediaTypeImageConfig.Validate(r, false)
 
 		if got := err != nil; tt.fail != got {
 			t.Errorf("test %d: expected validation failure %t but got %t, err %v", i, tt.fail, got, err)
diff --git a/schema/manifest_test.go b/schema/manifest_test.go
index f1cb51d02..addd1d424 100644
--- a/schema/manifest_test.go
+++ b/schema/manifest_test.go
@@ -23,11 +23,13 @@ import (
 
 func TestManifest(t *testing.T) {
 	for i, tt := range []struct {
+		strict   bool
 		manifest string
 		fail     bool
 	}{
 		// expected failure: mediaType does not match pattern
 		{
+			strict: false,
 			manifest: `
 {
   "schemaVersion": 2,
@@ -39,6 +41,7 @@ func TestManifest(t *testing.T) {
 
 		// expected failure: config.size is a string, expected integer
 		{
+			strict: false,
 			manifest: `
 {
   "schemaVersion": 2,
@@ -56,6 +59,7 @@ func TestManifest(t *testing.T) {
 
 		// expected failure: layers.size is string, expected integer
 		{
+			strict: false,
 			manifest: `
 {
   "schemaVersion": 2,
@@ -79,6 +83,7 @@ func TestManifest(t *testing.T) {
 
 		// valid manifest
 		{
+			strict: true,
 			manifest: `
 {
   "schemaVersion": 2,
@@ -115,7 +120,7 @@ func TestManifest(t *testing.T) {
 		},
 	} {
 		r := strings.NewReader(tt.manifest)
-		err := schema.MediaTypeManifest.Validate(r)
+		err := schema.MediaTypeManifest.Validate(r, tt.strict)
 
 		if got := err != nil; tt.fail != got {
 			t.Errorf("test %d: expected validation failure %t but got %t, err %v", i, tt.fail, got, err)
diff --git a/schema/spec_test.go b/schema/spec_test.go
index 2a6f4a493..c84c3fa7b 100644
--- a/schema/spec_test.go
+++ b/schema/spec_test.go
@@ -73,7 +73,7 @@ func validate(t *testing.T, name string) {
 			continue
 		}
 
-		err = schema.Validator(example.Mediatype).Validate(strings.NewReader(example.Body))
+		err = schema.Validator(example.Mediatype).Validate(strings.NewReader(example.Body), false)
 		if err == nil {
 			printFields(t, "ok", example.Mediatype, example.Title)
 			t.Log(example.Body, "---")
diff --git a/schema/validator.go b/schema/validator.go
index 432e7b992..0b491a320 100644
--- a/schema/validator.go
+++ b/schema/validator.go
@@ -30,7 +30,7 @@ import (
 // and implements validation against a JSON schema.
 type Validator string
 
-type validateDescendantsFunc func(r io.Reader) error
+type validateDescendantsFunc func(r io.Reader, strict bool) error
 
 var mapValidateDescendants = map[Validator]validateDescendantsFunc{
 	MediaTypeManifest: validateManifestDescendants,
@@ -46,7 +46,8 @@ func (e ValidationError) Error() string {
 }
 
 // Validate validates the given reader against the schema of the wrapped media type.
-func (v Validator) Validate(src io.Reader) error {
+// strict: accept the customized media type when value is false, or reject when true.
+func (v Validator) Validate(src io.Reader, strict bool) error {
 	buf, err := ioutil.ReadAll(src)
 	if err != nil {
 		return errors.Wrap(err, "unable to read the document file")
@@ -56,7 +57,7 @@ func (v Validator) Validate(src io.Reader) error {
 		if f == nil {
 			return fmt.Errorf("internal error: mapValidateDescendents[%q] is nil", v)
 		}
-		err = f(bytes.NewReader(buf))
+		err = f(bytes.NewReader(buf), strict)
 		if err != nil {
 			return err
 		}
@@ -88,11 +89,11 @@ func (v Validator) Validate(src io.Reader) error {
 
 type unimplemented string
 
-func (v unimplemented) Validate(src io.Reader) error {
+func (v unimplemented) Validate(src io.Reader, strict bool) error {
 	return fmt.Errorf("%s: unimplemented", v)
 }
 
-func validateManifestDescendants(r io.Reader) error {
+func validateManifestDescendants(r io.Reader, strict bool) error {
 	header := v1.Manifest{}
 
 	buf, err := ioutil.ReadAll(r)
@@ -106,13 +107,21 @@ func validateManifestDescendants(r io.Reader) error {
 	}
 
 	if header.Config.MediaType != string(v1.MediaTypeImageConfig) {
-		fmt.Printf("warning: config %s has an unknown media type: %s\n", header.Config.Digest, header.Config.MediaType)
+		msg := fmt.Sprintf("config %s has an unknown media type: %s", header.Config.Digest, header.Config.MediaType)
+		if strict {
+			return fmt.Errorf("%s", msg)
+		}
+		fmt.Printf("warning: %s\n", msg)
 	}
 
 	for _, layer := range header.Layers {
 		if layer.MediaType != string(v1.MediaTypeImageLayer) &&
 			layer.MediaType != string(v1.MediaTypeImageLayerNonDistributable) {
-			fmt.Printf("warning: layer %s has an unknown media type: %s\n", layer.Digest, layer.MediaType)
+			msg := fmt.Sprintf("layer %s has an unknown media type: %s", layer.Digest, layer.MediaType)
+			if strict {
+				return fmt.Errorf("%s", msg)
+			}
+			fmt.Printf("warning: %s\n", msg)
 		}
 	}
 	return nil