diff --git a/lib/zip_source_data.c b/lib/zip_source_data.c
index 2ed3669..56bf512 100644
--- a/lib/zip_source_data.c
+++ b/lib/zip_source_data.c
@@ -1,5 +1,5 @@
 /*
-  $NiH: zip_source_data.c,v 1.17 2004/11/17 21:55:13 wiz Exp $
+  $NiH: zip_source_data.c,v 1.1 2004/11/18 15:06:23 wiz Exp $
 
   zip_source_data.c -- create zip data source from buffer
   Copyright (C) 1999, 2003, 2004 Dieter Baron and Thomas Klausner
@@ -58,6 +58,9 @@
     struct read_data *f;
     struct zip_source *zs;
 
+    if (za == NULL)
+	return NULL;
+
     if (len < 0 || (data == NULL && len > 0)) {
 	_zip_error_set(&za->error, ZIP_ER_INVAL, 0);
 	return NULL;