diff --git a/specs-go/v1/index.go b/specs-go/v1/index.go
index 17a3859cb..c7d56ef66 100644
--- a/specs-go/v1/index.go
+++ b/specs-go/v1/index.go
@@ -47,7 +47,7 @@ type ManifestDescriptor struct {
 	Descriptor
 
 	// Platform describes the platform which the image in the manifest runs on.
-	Platform Platform `json:"platform"`
+	Platform Platform `json:"platform,omitempty"`
 }
 
 // Index references manifests for various platforms.