diff --git a/pkg/apitype/types.go b/pkg/apitype/types.go
index 8f7e01a9d..88a5fdf08 100644
--- a/pkg/apitype/types.go
+++ b/pkg/apitype/types.go
@@ -68,7 +68,7 @@ const (
 
 // UpdateEvent describes an event that happened on the Pulumi Cloud while processing an update.
 type UpdateEvent struct {
-	Index  int                    `json:"index"`
+	Index  string                 `json:"index"`
 	Kind   string                 `json:"kind"`
 	Fields map[string]interface{} `json:"fields"`
 }