diff --git a/schema/manifest_test.go b/schema/manifest_test.go
index f1cb51d02..5b57b09de 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,
@@ -113,9 +118,81 @@ func TestManifest(t *testing.T) {
 `,
 			fail: false,
 		},
+
+		// valid manifest accepts customized config media types
+		{
+			strict: false,
+			manifest: `
+{
+  "schemaVersion": 2,
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "config": {
+    "mediaType": "application/vnd.customized.config+json",
+    "size": 1470,
+    "digest": "sha256:c86f7763873b6c0aae22d963bab59b4f5debbed6685761b5951584f6efb0633b"
+  },
+  "layers": [
+    {
+      "mediaType": "application/vnd.customized.layer.tar+gzip",
+      "size": 148,
+      "digest": "sha256:c57089565e894899735d458f0fd4bb17a0f1e0df8d72da392b85c9b35ee777cd"
+    }
+  ]
+}
+`,
+			fail: false,
+		},
+
+		// expected failure strictly: unknown config.mediaType
+		{
+			strict: true,
+			manifest: `
+{
+  "schemaVersion": 2,
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "config": {
+    "mediaType": "application/vnd.customized.config+json",
+    "size": 1470,
+    "digest": "sha256:c86f7763873b6c0aae22d963bab59b4f5debbed6685761b5951584f6efb0633b"
+  },
+  "layers": [
+    {
+      "mediaType": "application/vnd.customized.layer.tar+gzip",
+      "size": 148,
+      "digest": "sha256:c57089565e894899735d458f0fd4bb17a0f1e0df8d72da392b85c9b35ee777cd"
+    }
+  ]
+}
+`,
+			fail: true,
+		},
+
+		// expected failure strictly: unknown layers[].mediaType
+		{
+			strict: true,
+			manifest: `
+{
+  "schemaVersion": 2,
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "config": {
+    "mediaType": "application/vnd.oci.image.config.v1+json",
+    "size": 1470,
+    "digest": "sha256:c86f7763873b6c0aae22d963bab59b4f5debbed6685761b5951584f6efb0633b"
+  },
+  "layers": [
+    {
+      "mediaType": "application/vnd.customized.layer.tar+gzip",
+      "size": 148,
+      "digest": "sha256:c57089565e894899735d458f0fd4bb17a0f1e0df8d72da392b85c9b35ee777cd"
+    }
+  ]
+}
+`,
+			fail: true,
+		},
 	} {
 		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/manifestlist_test.go b/schema/manifestlist_test.go
new file mode 100644
index 000000000..716fa6fee
--- /dev/null
+++ b/schema/manifestlist_test.go
@@ -0,0 +1,83 @@
+// Copyright 2016 The Linux Foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package schema_test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/opencontainers/image-spec/schema"
+)
+
+func TestManifestList(t *testing.T) {
+	for i, tt := range []struct {
+		strict       bool
+		manifestList string
+		fail         bool
+	}{
+		// valid manifest list accepting customized media types
+		{
+			strict: false,
+			manifestList: `
+{
+  "schemaVersion": 2,
+  "mediaType": "application/vnd.oci.image.manifest.list.v1+json",
+  "manifests": [
+    {
+      "mediaType": "application/customized+json",
+      "size": 7143,
+      "digest": "sha256:e692418e4cbaf90ca69d05a66403747baa33ee08806650b51fab815ad7fc331f",
+      "platform": {
+        "architecture": "ppc64le",
+        "os": "linux"
+      }
+    }
+  ]
+}
+`,
+			fail: false,
+		},
+
+		// expected failure strictly: manifests[].mediaType is unknown
+		{
+			strict: true,
+			manifestList: `
+{
+  "schemaVersion": 2,
+  "mediaType": "application/vnd.oci.image.manifest.list.v1+json",
+  "manifests": [
+    {
+      "mediaType": "application/customized+json",
+      "size": 7143,
+      "digest": "sha256:e692418e4cbaf90ca69d05a66403747baa33ee08806650b51fab815ad7fc331f",
+      "platform": {
+        "architecture": "ppc64le",
+        "os": "linux"
+      }
+    }
+  ]
+}
+`,
+			fail: true,
+		},
+	} {
+		r := strings.NewReader(tt.manifestList)
+		err := schema.MediaTypeManifestList.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)
+		}
+	}
+}