diff --git a/main/render.h b/main/render.h
index 197ed8560..3cb503473 100644
--- a/main/render.h
+++ b/main/render.h
@@ -54,7 +54,7 @@ extern fix Render_zoom;		//the player's zoom factor
 
 //This is used internally to render_frame(), but is included here so AI
 //can use it for its own purposes.
-extern char visited[MAX_SEGMENTS];
+extern unsigned char visited[MAX_SEGMENTS];
 
 extern int N_render_segs;
 extern short Render_list[MAX_RENDER_SEGS];