diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index f200c15f..ab4a8fff 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -228,7 +228,8 @@ typedef struct {
   XML_Bool keepProcessing;
   /* indicates if external PE has been read */
   XML_Bool paramEntityRead;
-  /* true once an internal or external PE reference has been encountered */
+  /* true once an internal or external PE reference has been encountered;
+     any external subset is considered an external PE reference */
   XML_Bool hasParamEntityRefs;
   XML_Bool standalone;
 #ifdef XML_DTD