diff --git a/engine/gl/gl_vidnt.c b/engine/gl/gl_vidnt.c
index 0dbd1ec2..b241f09a 100644
--- a/engine/gl/gl_vidnt.c
+++ b/engine/gl/gl_vidnt.c
@@ -825,6 +825,8 @@ void	GLVID_SetPalette (unsigned char *palette)
 	d_8to24rgbtable[255] &= 0xffffff;	// 255 is transparent
 }
 
+extern gammaworks;
+
 void	GLVID_ShiftPalette (unsigned char *palette)
 {
 	extern	unsigned short ramps[3][256];