diff --git a/manifest/manifestlist/manifestlist.go b/manifest/manifestlist/manifestlist.go
index 25ffbe525..10474e679 100644
--- a/manifest/manifestlist/manifestlist.go
+++ b/manifest/manifestlist/manifestlist.go
@@ -24,29 +24,28 @@ var SchemaVersion = manifest.Versioned{
 }
 
 func init() {
-	manifestListFunc := func(b []byte) (distribution.Manifest, distribution.Descriptor, error) {
-		m := new(DeserializedManifestList)
-		err := m.UnmarshalJSON(b)
-		if err != nil {
-			return nil, distribution.Descriptor{}, err
-		}
-
-		if m.MediaType != MediaTypeManifestList {
-			err = fmt.Errorf("mediaType in manifest list should be '%s' not '%s'",
-				MediaTypeManifestList, m.MediaType)
-
-			return nil, distribution.Descriptor{}, err
-		}
-
-		dgst := digest.FromBytes(b)
-		return m, distribution.Descriptor{Digest: dgst, Size: int64(len(b)), MediaType: MediaTypeManifestList}, err
-	}
-	err := distribution.RegisterManifestSchema(MediaTypeManifestList, manifestListFunc)
-	if err != nil {
+	if err := distribution.RegisterManifestSchema(MediaTypeManifestList, unmarshalManifestList); err != nil {
 		panic(fmt.Sprintf("Unable to register manifest: %s", err))
 	}
 }
 
+func unmarshalManifestList(b []byte) (distribution.Manifest, distribution.Descriptor, error) {
+	m := &DeserializedManifestList{}
+	if err := m.UnmarshalJSON(b); err != nil {
+		return nil, distribution.Descriptor{}, err
+	}
+
+	if m.MediaType != MediaTypeManifestList {
+		return nil, distribution.Descriptor{}, fmt.Errorf("mediaType in manifest list should be '%s' not '%s'", MediaTypeManifestList, m.MediaType)
+	}
+
+	return m, distribution.Descriptor{
+		Digest:    digest.FromBytes(b),
+		Size:      int64(len(b)),
+		MediaType: MediaTypeManifestList,
+	}, nil
+}
+
 // PlatformSpec specifies a platform where a particular image manifest is
 // applicable.
 type PlatformSpec struct {
diff --git a/manifest/ocischema/index.go b/manifest/ocischema/index.go
index 834b02ab6..d4ec31456 100644
--- a/manifest/ocischema/index.go
+++ b/manifest/ocischema/index.go
@@ -19,37 +19,33 @@ var IndexSchemaVersion = manifest.Versioned{
 }
 
 func init() {
-	imageIndexFunc := func(b []byte) (distribution.Manifest, distribution.Descriptor, error) {
-		if err := validateIndex(b); err != nil {
-			return nil, distribution.Descriptor{}, err
-		}
-		m := new(DeserializedImageIndex)
-		err := m.UnmarshalJSON(b)
-		if err != nil {
-			return nil, distribution.Descriptor{}, err
-		}
-
-		if m.MediaType != "" && m.MediaType != v1.MediaTypeImageIndex {
-			err = fmt.Errorf("if present, mediaType in image index should be '%s' not '%s'",
-				v1.MediaTypeImageIndex, m.MediaType)
-
-			return nil, distribution.Descriptor{}, err
-		}
-
-		dgst := digest.FromBytes(b)
-		return m, distribution.Descriptor{
-			MediaType:   v1.MediaTypeImageIndex,
-			Digest:      dgst,
-			Size:        int64(len(b)),
-			Annotations: m.Annotations,
-		}, err
-	}
-	err := distribution.RegisterManifestSchema(v1.MediaTypeImageIndex, imageIndexFunc)
-	if err != nil {
+	if err := distribution.RegisterManifestSchema(v1.MediaTypeImageIndex, unmarshalImageIndex); err != nil {
 		panic(fmt.Sprintf("Unable to register OCI Image Index: %s", err))
 	}
 }
 
+func unmarshalImageIndex(b []byte) (distribution.Manifest, distribution.Descriptor, error) {
+	if err := validateIndex(b); err != nil {
+		return nil, distribution.Descriptor{}, err
+	}
+
+	m := &DeserializedImageIndex{}
+	if err := m.UnmarshalJSON(b); err != nil {
+		return nil, distribution.Descriptor{}, err
+	}
+
+	if m.MediaType != "" && m.MediaType != v1.MediaTypeImageIndex {
+		return nil, distribution.Descriptor{}, fmt.Errorf("if present, mediaType in image index should be '%s' not '%s'", v1.MediaTypeImageIndex, m.MediaType)
+	}
+
+	return m, distribution.Descriptor{
+		MediaType:   v1.MediaTypeImageIndex,
+		Digest:      digest.FromBytes(b),
+		Size:        int64(len(b)),
+		Annotations: m.Annotations,
+	}, nil
+}
+
 // ImageIndex references manifests for various platforms.
 type ImageIndex struct {
 	manifest.Versioned
diff --git a/manifest/ocischema/manifest.go b/manifest/ocischema/manifest.go
index ab793afc9..e409a90f1 100644
--- a/manifest/ocischema/manifest.go
+++ b/manifest/ocischema/manifest.go
@@ -19,30 +19,29 @@ var SchemaVersion = manifest.Versioned{
 }
 
 func init() {
-	ocischemaFunc := func(b []byte) (distribution.Manifest, distribution.Descriptor, error) {
-		if err := validateManifest(b); err != nil {
-			return nil, distribution.Descriptor{}, err
-		}
-		m := new(DeserializedManifest)
-		err := m.UnmarshalJSON(b)
-		if err != nil {
-			return nil, distribution.Descriptor{}, err
-		}
-
-		dgst := digest.FromBytes(b)
-		return m, distribution.Descriptor{
-			MediaType:   v1.MediaTypeImageManifest,
-			Digest:      dgst,
-			Size:        int64(len(b)),
-			Annotations: m.Annotations,
-		}, err
-	}
-	err := distribution.RegisterManifestSchema(v1.MediaTypeImageManifest, ocischemaFunc)
-	if err != nil {
+	if err := distribution.RegisterManifestSchema(v1.MediaTypeImageManifest, unmarshalOCISchema); err != nil {
 		panic(fmt.Sprintf("Unable to register manifest: %s", err))
 	}
 }
 
+func unmarshalOCISchema(b []byte) (distribution.Manifest, distribution.Descriptor, error) {
+	if err := validateManifest(b); err != nil {
+		return nil, distribution.Descriptor{}, err
+	}
+
+	m := &DeserializedManifest{}
+	if err := m.UnmarshalJSON(b); err != nil {
+		return nil, distribution.Descriptor{}, err
+	}
+
+	return m, distribution.Descriptor{
+		MediaType:   v1.MediaTypeImageManifest,
+		Digest:      digest.FromBytes(b),
+		Size:        int64(len(b)),
+		Annotations: m.Annotations,
+	}, nil
+}
+
 // Manifest defines a ocischema manifest.
 type Manifest struct {
 	manifest.Versioned
diff --git a/manifest/schema2/manifest.go b/manifest/schema2/manifest.go
index 89bf63c96..f918c6379 100644
--- a/manifest/schema2/manifest.go
+++ b/manifest/schema2/manifest.go
@@ -41,22 +41,24 @@ var SchemaVersion = manifest.Versioned{
 }
 
 func init() {
-	schema2Func := func(b []byte) (distribution.Manifest, distribution.Descriptor, error) {
-		m := new(DeserializedManifest)
-		err := m.UnmarshalJSON(b)
-		if err != nil {
-			return nil, distribution.Descriptor{}, err
-		}
-
-		dgst := digest.FromBytes(b)
-		return m, distribution.Descriptor{Digest: dgst, Size: int64(len(b)), MediaType: MediaTypeManifest}, err
-	}
-	err := distribution.RegisterManifestSchema(MediaTypeManifest, schema2Func)
-	if err != nil {
+	if err := distribution.RegisterManifestSchema(MediaTypeManifest, unmarshalSchema2); err != nil {
 		panic(fmt.Sprintf("Unable to register manifest: %s", err))
 	}
 }
 
+func unmarshalSchema2(b []byte) (distribution.Manifest, distribution.Descriptor, error) {
+	m := &DeserializedManifest{}
+	if err := m.UnmarshalJSON(b); err != nil {
+		return nil, distribution.Descriptor{}, err
+	}
+
+	return m, distribution.Descriptor{
+		Digest:    digest.FromBytes(b),
+		Size:      int64(len(b)),
+		MediaType: MediaTypeManifest,
+	}, nil
+}
+
 // Manifest defines a schema2 manifest.
 type Manifest struct {
 	manifest.Versioned