diff --git a/pep-0633.rst b/pep-0633.rst
index 9ffbcad74..1f1720718 100644
--- a/pep-0633.rst
+++ b/pep-0633.rst
@@ -183,9 +183,9 @@ performed):
             pep508 += " @ " + requirement["url"]
         for vcs in ("git", "hg", "bzr", "svn"):
             if vcs in requirement:
-                pep508 += " @ " + vcs + "+" requirement[vcs]
+                pep508 += " @ " + vcs + "+" + requirement[vcs]
                 if "revision" in requirement:
-                    pep508 += "@" + revision
+                    pep508 += "@" + requirement["revision"]
         extra = None
         if "for-extra" in requirement:
             extra = requirement["for-extra"]
@@ -199,19 +199,19 @@ performed):
 
     def convert_requirements_to_pep508(dependencies):
         pep508s = []
-        extras = []
+        extras = set()
         for name, req in dependencies.items():
             if isinstance(req, list):
                 for sub_req in req:
                     pep508, extra = convert_requirement_to_pep508(name, sub_req)
                     pep508s.append(pep508)
                     if extra:
-                        extras.append(extra)
+                        extras.add(extra)
             else:
-                pep508, extra = convert_requirement_to_pep508(name, sub_req)
+                pep508, extra = convert_requirement_to_pep508(name, req)
                 pep508s.append(pep508)
                 if extra:
-                    extras.append(extra)
+                    extras.add(extra)
         return pep508s, extras
 
 
@@ -233,7 +233,7 @@ validation errors as users are building the dependencies list.
 .. code-block::
 
     {
-        "$id": "http://sitesee.com.au/schemas/equipment/v3.json",
+        "$id": "spam",
         "$schema": "http://json-schema.org/draft-07/schema#",
         "title": "Project metadata",
         "type": "object",
@@ -255,6 +255,19 @@ validation errors as users are building the dependencies list.
                         "type": "string"
                     }
                 },
+                "propertyNames": {
+                    "enum": [
+                        "extras",
+                        "markers",
+                        "version",
+                        "url",
+                        "git",
+                        "hg",
+                        "bzr",
+                        "svn",
+                        "for-extra"
+                    ]
+                },
                 "oneOf": [
                     {
                         "title": "Version requirement",
@@ -366,24 +379,11 @@ validation errors as users are building the dependencies list.
                     }
                 ]
             },
-            "optionalRequirement": {
-                "title": "Project optional dependency specification",
+            "optionalRequirementTable": {
+                "title": "Project optional dependency specification table",
                 "allOf": [
                     {
-                        "title": "Base requirement",
-                        "oneOf": [
-                            {
-                                "$ref": "#/definitions/requirementTable"
-                            },
-                            {
-                                "title": "Multiple specifications",
-                                "type": "array",
-                                "items": {
-                                    "$ref": "#/definitions/requirementTable"
-                                },
-                                "minLength": 1
-                            }
-                        ]
+                        "$ref": "#/definitions/requirementTable"
                     },
                     {
                         "properties": {
@@ -397,6 +397,22 @@ validation errors as users are building the dependencies list.
                         ]
                     }
                 ]
+            },
+            "optionalRequirement": {
+                "title": "Project optional dependency specification",
+                "oneOf": [
+                    {
+                        "$ref": "#/definitions/optionalRequirementTable"
+                    },
+                    {
+                        "title": "Multiple specifications",
+                        "type": "array",
+                        "items": {
+                            "$ref": "#/definitions/optionalRequirementTable"
+                        },
+                        "minLength": 1
+                    }
+                ]
             }
         },
         "properties": {