diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index 4be9aad48e26931022663801e0123f479792e899..408a662ea58f329f643dcdc986014afb51433776 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -846,7 +846,7 @@
 ##
 # @GuestDiskAddress:
 #
-# @pci-controller: controller's PCI address
+# @pci-controller: controller's PCI address (fields are set to -1 if invalid)
 # @bus-type: bus type
 # @bus: bus id
 # @target: target id