+++ clientgui/AsyncRPC.cpp
--- clientgui/AsyncRPC.cpp
@@ -19,7 +19,7 @@
 #pragma implementation "AsyncRPC.h"
 #endif
 
-#if !(defined(_WIN32) || (defined(__WXMAC__) && (MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_4)))
+#if HAVE_XLOCALE_H
 #include <xlocale.h>
 #endif

+++ lib/gui_rpc_client.h
--- lib/gui_rpc_client.h
@@ -809,7 +809,9 @@ struct RPC {
 
 #elif defined(__APPLE__) && (MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_4)
 // uselocale() is not available in OS 10.3.9 so use weak linking
+#if HAVE_XLOCALE_H
 #include <xlocale.h>
+#endif
 extern int		freelocale(locale_t) __attribute__((weak_import));
 extern locale_t	newlocale(int, __const char *, locale_t) __attribute__((weak_import));
 extern locale_t	uselocale(locale_t) __attribute__((weak_import));