diff --git a/doc/spec/api.md b/doc/spec/api.md
index 9aa6794bc..d42b56742 100644
--- a/doc/spec/api.md
+++ b/doc/spec/api.md
@@ -2035,7 +2035,7 @@ The following parameters should be specified on the request:
 |`Host`|header|Standard HTTP Host Header. Should be set to the registry host.|
 |`Authorization`|header|An RFC7235 compliant authorization header.|
 |`name`|path|Name of the target repository.|
-|`uuid`|path|A uuid identifying the upload. This field can accept almost anything.|
+|`uuid`|path|A uuid identifying the upload. This field can accept characters that match `[a-zA-Z0-9-_.=]+`.|
 
 
 
@@ -2193,7 +2193,7 @@ The following parameters should be specified on the request:
 |`Content-Range`|header|Range of bytes identifying the desired block of content represented by the body. Start must the end offset retrieved via status check plus one. Note that this is a non-standard use of the `Content-Range` header.|
 |`Content-Length`|header|Length of the chunk being uploaded, corresponding the length of the request body.|
 |`name`|path|Name of the target repository.|
-|`uuid`|path|A uuid identifying the upload. This field can accept almost anything.|
+|`uuid`|path|A uuid identifying the upload. This field can accept characters that match `[a-zA-Z0-9-_.=]+`.|
 
 
 
@@ -2363,7 +2363,7 @@ The following parameters should be specified on the request:
 |`Content-Range`|header|Range of bytes identifying the block of content represented by the body. Start must the end offset retrieved via status check plus one. Note that this is a non-standard use of the `Content-Range` header. May be omitted if no data is provided.|
 |`Content-Length`|header|Length of the chunk being uploaded, corresponding to the length of the request body. May be zero if no data is provided.|
 |`name`|path|Name of the target repository.|
-|`uuid`|path|A uuid identifying the upload. This field can accept almost anything.|
+|`uuid`|path|A uuid identifying the upload. This field can accept characters that match `[a-zA-Z0-9-_.=]+`.|
 |`digest`|query|Digest of uploaded blob.|
 
 
@@ -2538,7 +2538,7 @@ The following parameters should be specified on the request:
 |`Authorization`|header|An RFC7235 compliant authorization header.|
 |`Content-Length`|header|The `Content-Length` header must be zero and the body must be empty.|
 |`name`|path|Name of the target repository.|
-|`uuid`|path|A uuid identifying the upload. This field can accept almost anything.|
+|`uuid`|path|A uuid identifying the upload. This field can accept characters that match `[a-zA-Z0-9-_.=]+`.|
 
 
 
diff --git a/registry/api/v2/descriptors.go b/registry/api/v2/descriptors.go
index 5f091bbc9..73f8b463e 100644
--- a/registry/api/v2/descriptors.go
+++ b/registry/api/v2/descriptors.go
@@ -28,7 +28,7 @@ var (
 		Name:        "uuid",
 		Type:        "opaque",
 		Required:    true,
-		Description: `A uuid identifying the upload. This field can accept almost anything.`,
+		Description: "A uuid identifying the upload. This field can accept characters that match `[a-zA-Z0-9-_.=]+`.",
 	}
 
 	digestPathParameter = ParameterDescriptor{
@@ -985,7 +985,7 @@ var routeDescriptors = []RouteDescriptor{
 
 	{
 		Name:        RouteNameBlobUploadChunk,
-		Path:        "/v2/{name:" + RepositoryNameRegexp.String() + "}/blobs/uploads/{uuid}",
+		Path:        "/v2/{name:" + RepositoryNameRegexp.String() + "}/blobs/uploads/{uuid:[a-zA-Z0-9-_.=]+}",
 		Entity:      "Blob Upload",
 		Description: "Interact with blob uploads. Clients should never assemble URLs for this endpoint and should only take it through the `Location` header on related API requests. The `Location` header and its parameters should be preserved by clients, using the latest value returned via upload related API calls.",
 		Methods: []MethodDescriptor{
diff --git a/registry/api/v2/routes_test.go b/registry/api/v2/routes_test.go
index afab71fce..fb268336f 100644
--- a/registry/api/v2/routes_test.go
+++ b/registry/api/v2/routes_test.go
@@ -98,6 +98,7 @@ func TestRouter(t *testing.T) {
 			},
 		},
 		{
+			// support uuid proper
 			RouteName:  RouteNameBlobUploadChunk,
 			RequestURI: "/v2/foo/bar/blobs/uploads/D95306FA-FAD3-4E36-8D41-CF1C93EF8286",
 			Vars: map[string]string{
@@ -113,6 +114,21 @@ func TestRouter(t *testing.T) {
 				"uuid": "RDk1MzA2RkEtRkFEMy00RTM2LThENDEtQ0YxQzkzRUY4Mjg2IA==",
 			},
 		},
+		{
+			// supports urlsafe base64
+			RouteName:  RouteNameBlobUploadChunk,
+			RequestURI: "/v2/foo/bar/blobs/uploads/RDk1MzA2RkEtRkFEMy00RTM2LThENDEtQ0YxQzkzRUY4Mjg2IA_-==",
+			Vars: map[string]string{
+				"name": "foo/bar",
+				"uuid": "RDk1MzA2RkEtRkFEMy00RTM2LThENDEtQ0YxQzkzRUY4Mjg2IA_-==",
+			},
+		},
+		{
+			// does not match
+			RouteName:  RouteNameBlobUploadChunk,
+			RequestURI: "/v2/foo/bar/blobs/uploads/totalandcompletejunk++$$-==",
+			StatusCode: http.StatusNotFound,
+		},
 		{
 			// Check ambiguity: ensure we can distinguish between tags for
 			// "foo/bar/image/image" and image for "foo/bar/image" with tag