diff --git a/hw/kdrive/ephyr/os.c b/hw/kdrive/ephyr/os.c
index b58daae68..4bf6e8858 100644
--- a/hw/kdrive/ephyr/os.c
+++ b/hw/kdrive/ephyr/os.c
@@ -28,6 +28,8 @@
 #endif
 #include "ephyr.h"
 
+extern void processScreenArg (char *screen_size, char *parent_id) ;
+
 static int
 EphyrInit (void)
 {