diff --git a/source/d_edge.c b/source/d_edge.c
index 3085252..9960bbe 100644
--- a/source/d_edge.c
+++ b/source/d_edge.c
@@ -32,7 +32,7 @@
 static int	miplevel;
 
 float		scale_for_mip;
-int			screenwidth;
+extern int	screenwidth;
 int			ubasestep, errorterm, erroradjustup, erroradjustdown;
 int			vstartscan;
 
diff --git a/source/gl_vidnt.c b/source/gl_vidnt.c
index bd6b35e..244e057 100644
--- a/source/gl_vidnt.c
+++ b/source/gl_vidnt.c
@@ -76,7 +76,7 @@ const char *gl_version;
 const char *gl_extensions;
 
 qboolean		DDActive;
-qboolean		scr_skipupdate;
+extern qboolean	scr_skipupdate;
 
 static vmode_t	modelist[MAX_MODE_LIST];
 static int		nummodes;
diff --git a/source/gl_warp.c b/source/gl_warp.c
index 52f4fdb..580cfa8 100644
--- a/source/gl_warp.c
+++ b/source/gl_warp.c
@@ -54,7 +54,7 @@
 extern	double	realtime;
 extern	model_t	*loadmodel;
 
-int		skytexturenum;
+extern	int		skytexturenum;
 
 int		solidskytexture;
 int		alphaskytexture;