diff --git a/compat/getopt_long.c b/compat/getopt_long.c
index 3d4df3fc..fdbcc86f 100644
--- a/compat/getopt_long.c
+++ b/compat/getopt_long.c
@@ -339,7 +339,7 @@ static int
 getopt_internal(int nargc, char * const *nargv, const char *options,
 	const struct option *long_options, int *idx, int flags)
 {
-	char *oli;				/* option letter list index */
+	const char *oli;			/* option letter list index */
 	int optchar, short_too;
 	static int posixly_correct = -1;