diff --git a/winsup/w32api/ChangeLog b/winsup/w32api/ChangeLog
index 425b4ebb6..07661ed9a 100644
--- a/winsup/w32api/ChangeLog
+++ b/winsup/w32api/ChangeLog
@@ -1,3 +1,9 @@
+Thu Jun 22 14:36:19 2000  Christopher Faylor <cgf@cygnus.com>
+
+	* rpcdce.h: Protect OPTIONAL definition since it may be (legally)
+	previously defined.
+	* windef.h : Ditto.
+
 2000-06-14  Kazuhiro Fujieda <fujieda@jaist.ac.jp>
 
 	* include/winnt.h: Add some missing defines related to locale
diff --git a/winsup/w32api/include/rpcdce.h b/winsup/w32api/include/rpcdce.h
index 97d93ce59..e07fa3a9d 100644
--- a/winsup/w32api/include/rpcdce.h
+++ b/winsup/w32api/include/rpcdce.h
@@ -8,7 +8,9 @@ extern "C" {
 
 #define IN
 #define OUT
+#ifndef OPTIONAL
 #define OPTIONAL
+#endif
 #define uuid_t UUID
 #define rpc_binding_handle_t RPC_BINDING_HANDLE
 #define rpc_binding_vector_t RPC_BINDING_VECTOR
diff --git a/winsup/w32api/include/windef.h b/winsup/w32api/include/windef.h
index 433cacfbb..129a9a7d7 100644
--- a/winsup/w32api/include/windef.h
+++ b/winsup/w32api/include/windef.h
@@ -41,7 +41,9 @@ extern "C" {
 #endif
 #define IN
 #define OUT
+#ifndef OPTIONAL
 #define OPTIONAL
+#endif
 
 #ifdef __GNUC__
 #define PACKED __attribute__((packed))