--- ray/src/rt/rv2.c	1993/09/09 13:47:55	2.20
+++ ray/src/rt/rv2.c	1993/09/09 14:57:53	2.21
@@ -32,6 +32,8 @@ static char SCCSid[] = "$SunId$ LBL";
 
 extern char  *atos();
 
+extern FILE  *popen();
+
 extern char  rifname[128];		/* rad input file name */
 
 extern char  VersionID[];