diff --git a/lib/modules/datasource/docker/index.ts b/lib/modules/datasource/docker/index.ts
index 6c539394ad31ba1bfb17f741573a5f9ca0661963..c7f7828315545670cce78d5708371281145ea38f 100644
--- a/lib/modules/datasource/docker/index.ts
+++ b/lib/modules/datasource/docker/index.ts
@@ -515,8 +515,7 @@ export class DockerDatasource extends Datasource {
       manifest.mediaType === MediaType.ociManifestIndexV1 ||
       (!manifest.mediaType && hasKey('manifests', manifest))
     ) {
-      const imageList = manifest;
-      if (imageList.manifests.length) {
+      if (manifest.manifests.length) {
         logger.trace(
           { registry, dockerRepository, tag },
           'Found manifest index, using first image'
diff --git a/lib/modules/datasource/docker/types.ts b/lib/modules/datasource/docker/types.ts
index a3e1350a424666f81bf525652deb3c71bbb8934b..4e390ea27e2040d9fafb31f86665d8d70e4b43f7 100644
--- a/lib/modules/datasource/docker/types.ts
+++ b/lib/modules/datasource/docker/types.ts
@@ -24,7 +24,7 @@ export interface MediaObject {
 export interface ImageListImage extends MediaObject {
   readonly mediaType: MediaType.manifestV1 | MediaType.manifestV2;
 
-  readonly platform: Record<string, unknown>;
+  readonly platform: OciPlatform;
 }
 
 /**
@@ -48,6 +48,19 @@ export interface Image extends MediaObject {
   readonly config: MediaObject;
 }
 
+/**
+ * OCI platform properties
+ * https://github.com/opencontainers/image-spec/blob/main/image-index.md
+ */
+export interface OciPlatform {
+  architecture?: string;
+  features?: string[];
+  os?: string;
+  'os.features'?: string[];
+  'os.version'?: string;
+  variant?: string;
+}
+
 /**
  * OCI content descriptor
  * https://github.com/opencontainers/image-spec/blob/main/descriptor.md
@@ -75,7 +88,7 @@ export interface OciImage {
 
 export interface OciImageListManifest extends OciDescriptor {
   readonly mediaType?: MediaType.ociManifestV1 | MediaType.ociManifestIndexV1;
-  readonly platform: Record<string, unknown>;
+  readonly platform: OciPlatform;
 }
 
 /**