diff --git a/src/video/vid_ati_mach64.c b/src/video/vid_ati_mach64.c
index f18c9b0e9..a96184b2b 100644
--- a/src/video/vid_ati_mach64.c
+++ b/src/video/vid_ati_mach64.c
@@ -2108,6 +2108,7 @@ uint8_t mach64_ext_readb(uint32_t addr, void *p)
 }
 uint16_t mach64_ext_readw(uint32_t addr, void *p)
 {
+        mach64_t *mach64 = (mach64_t *)p;
         uint16_t ret;
         if (!(addr & 0x400))
         {