diff --git a/lang/basic/src.old/basic.lex b/lang/basic/src.old/basic.lex
index b901ca63f..bb72e467a 100644
--- a/lang/basic/src.old/basic.lex
+++ b/lang/basic/src.old/basic.lex
@@ -141,6 +141,8 @@ Key keywords [] ={
 0,	0,	0,	0
 };
 
+char *index();
+
 /* Keyword index table */
 
 int	kex[27];
@@ -470,3 +472,13 @@ yylex()
 	}
 	return(*cptr++);
 }
+
+char *
+index(s, c)
+	register char *s, c;
+{
+	while (*s)
+		if (*s++ == c)
+			return --s;
+	return (char *)0;
+}