diff --git a/headers/private/graphics/via/macros.h b/headers/private/graphics/via/macros.h
index 65feef3a7c..09fb2de7a1 100644
--- a/headers/private/graphics/via/macros.h
+++ b/headers/private/graphics/via/macros.h
@@ -583,6 +583,7 @@
 #define ENCRTCX_VTIMEXT_PIT	0x35
 #define ENCRTCX_HTIMEXT2	0x36
 #define ENCRTCX_TVTYPE		0x3b //TVtype jumper: b1=1 = PAL, else NTSC
+#define ENCRTCX_MEMCLK		0x3d
 //end via
 /* Nvidia specific registers: */
 #define ENCRTCX_REPAINT0	0x19