diff --git a/descriptor.md b/descriptor.md
index f14d7cb48..4bc5e0414 100644
--- a/descriptor.md
+++ b/descriptor.md
@@ -19,7 +19,8 @@ The following fields contain the primary properties that constitute a Descriptor
 
 - **`mediaType`** *string*
 
-  This REQUIRED property contains the MIME type of the referenced content.
+  This REQUIRED property contains the media type of the referenced content.
+  Values MUST comply with [RFC 6838][rfc6838], including the [naming requirements in its section 4.2][rfc6838-s4.2].
 
   The OCI image specification defines [several of its own MIME types](media-types.md) for resources defined in the specification.
 
@@ -139,4 +140,6 @@ In the following example, the descriptor indicates that the referenced manifest
 ```
 
 [rfc3986]: https://tools.ietf.org/html/rfc3986
+[rfc6838]: https://tools.ietf.org/html/rfc6838
+[rfc6838-s4.2]: https://tools.ietf.org/html/rfc6838#section-4.2
 [rfc7230-s2.7]: https://tools.ietf.org/html/rfc7230#section-2.7
diff --git a/schema/descriptor_test.go b/schema/descriptor_test.go
new file mode 100644
index 000000000..68c35cead
--- /dev/null
+++ b/schema/descriptor_test.go
@@ -0,0 +1,213 @@
+// 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 TestDescriptor(t *testing.T) {
+	for i, tt := range []struct {
+		descriptor string
+		fail     bool
+	}{
+		// valid descriptor
+		{
+			descriptor: `
+{
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "size": 7682,
+  "digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: false,
+		},
+
+		// expected failure: mediaType missing
+		{
+			descriptor: `
+{
+  "size": 7682,
+  "digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: true,
+		},
+
+		// expected failure: mediaType does not match pattern (no subtype)
+		{
+			descriptor: `
+{
+  "mediaType": "application",
+  "size": 7682,
+  "digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: true,
+		},
+
+		// expected failure: mediaType does not match pattern (invalid first type character)
+		{
+			descriptor: `
+{
+  "mediaType": ".foo/bar",
+  "size": 7682,
+  "digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: true,
+		},
+
+		// expected failure: mediaType does not match pattern (invalid first subtype character)
+		{
+			descriptor: `
+{
+  "mediaType": "foo/.bar",
+  "size": 7682,
+  "digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: true,
+		},
+
+		// expected success: mediaType has type and subtype as long as possible
+		{
+			descriptor: `
+{
+  "mediaType": "1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567/1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567",
+  "size": 7682,
+  "digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: false,
+		},
+
+		// expected success: mediaType does not match pattern (type too long)
+		{
+			descriptor: `
+{
+  "mediaType": "12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678/bar",
+  "size": 7682,
+  "digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: true,
+		},
+
+		// expected success: mediaType does not match pattern (subtype too long)
+		{
+			descriptor: `
+{
+  "mediaType": "foo/12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678",
+  "size": 7682,
+  "digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: true,
+		},
+
+		// expected failure: size missing
+		{
+			descriptor: `
+{
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: true,
+		},
+
+		// expected failure: size is a string, expected integer
+		{
+			descriptor: `
+{
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "size": "7682",
+  "digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: true,
+		},
+
+		// expected failure: digest missing
+		{
+			descriptor: `
+{
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "size": 7682
+}
+`,
+			fail: true,
+		},
+
+		// expected failure: digest does not match pattern (no algorithm)
+		{
+			descriptor: `
+{
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "size": 7682,
+  "digest": ":5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: true,
+		},
+
+		// expected failure: digest does not match pattern (no hash)
+		{
+			descriptor: `
+{
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "size": 7682,
+  "digest": "sha256"
+}
+`,
+			fail: true,
+		},
+
+		// expected failure: digest does not match pattern (invalid aglorithm characters)
+		{
+			descriptor: `
+{
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "size": 7682,
+  "digest": "SHA256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
+}
+`,
+			fail: true,
+		},
+
+		// expected failure: digest does not match pattern (invalid hash characters)
+		{
+			descriptor: `
+{
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "size": 7682,
+  "digest": "sha256:5B0BCABD1ED22E9FB1310CF6C2DEC7CDEF19F0AD69EFA1F392E94A4333501270"
+}
+`,
+			fail: true,
+		},
+	} {
+		r := strings.NewReader(tt.descriptor)
+		err := schema.MediaTypeDescriptor.Validate(r)
+
+		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)
+		}
+	}
+}