diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 847a3c7fe..3d4140afb 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,7 @@
+2003-09-01  Christopher Faylor  <cgf@redhat.com>
+
+	* net.cc (dup_ent): Restore check for NULL input.
+
 2003-08-31  Christopher Faylor  <cgf@redhat.com>
 
 	* include/sys/cygwin.h: Don't define cygwin-specific things if
diff --git a/winsup/cygwin/net.cc b/winsup/cygwin/net.cc
index 79adfc3f6..b888ab60c 100644
--- a/winsup/cygwin/net.cc
+++ b/winsup/cygwin/net.cc
@@ -449,6 +449,9 @@ dup_ent (void *old, void *src0, struct_type type)
       free (old);
     }
 
+  if (!src0)
+    return NULL;
+
   unionent *src = (unionent *) src0;
   debug_printf ("duping %sent \"%s\", %p", entnames[type],
 		src ? src->name : "<null!>", src);