diff -Naur a/xmlschemas.c b/xmlschemas.c
--- a/xmlschemas.c	2023-04-26 11:44:01.081847541 +0800
+++ b/xmlschemas.c	2023-04-26 11:48:01.812564661 +0800
@@ -18608,7 +18608,7 @@
 			"allowed to appear inside other model groups",
 			NULL, NULL);
 
-		} else if (! dummySequence) {
+		} else if ((!dummySequence) && (baseType->subtypes != NULL)) {
 		    xmlSchemaTreeItemPtr effectiveContent =
 			(xmlSchemaTreeItemPtr) type->subtypes;
 		    /*