diff --git a/packages/workflow/src/Interfaces.ts b/packages/workflow/src/Interfaces.ts
index 0a94261cf8..5711de38ca 100644
--- a/packages/workflow/src/Interfaces.ts
+++ b/packages/workflow/src/Interfaces.ts
@@ -1184,6 +1184,11 @@ export interface INodeExecutionData {
 	metadata?: {
 		subExecution: RelatedExecution;
 	};
+
+	/**
+	 * @deprecated This key was added by accident and should not be used as it
+	 * will be removed in future. For more information see PR #12469.
+	 */
 	index?: number;
 }