diff --git a/lib/config/builder/value.ts b/lib/config/builder/value.ts
index cca028b..7f442be 100644
--- a/lib/config/builder/value.ts
+++ b/lib/config/builder/value.ts
@@ -145,7 +145,6 @@ export class Value<A extends ValueSpec> extends IBuilder<A> {
       name: string;
       description: string | null;
       warning: string | null;
-      selectKey: string;
       variants: Variants<{ [key: string]: { name: string; spec: InputSpec } }>;
       nullable: boolean;
       default: string | null;
diff --git a/lib/config/config-types.ts b/lib/config/config-types.ts
index b25fe18..5dfbb62 100644
--- a/lib/config/config-types.ts
+++ b/lib/config/config-types.ts
@@ -66,8 +66,7 @@ export interface ValueSpecBoolean extends WithStandalone {
 
 export interface ValueSpecUnion extends WithStandalone {
   type: "union";
-  selectKey: string;
-  nullable: boolean
+  nullable: boolean;
   variants: Record<string, { name: string; spec: InputSpec }>;
 }
 
diff --git a/scripts/oldSpecToBuilder.ts b/scripts/oldSpecToBuilder.ts
index 30e05f6..093e772 100644
--- a/scripts/oldSpecToBuilder.ts
+++ b/scripts/oldSpecToBuilder.ts
@@ -143,6 +143,7 @@ export default async function makeFileContent(
         name: ${JSON.stringify(value.name || null)},
         description: ${JSON.stringify(value.description || null)},
         warning: ${JSON.stringify(value.warning || null)},
+        nullable: false,
         default: ${JSON.stringify(value.default || null)},
         variants: ${variants},
       })`;