diff --git a/vncviewer/win32.h b/vncviewer/win32.h
index 0148708..9d4704b 100644
--- a/vncviewer/win32.h
+++ b/vncviewer/win32.h
@@ -32,6 +32,8 @@
 
 int win32_vkey_to_keysym(UINT vkey, int extended);
 
+int win32_has_altgr(void);
+
 };
 
 #endif