diff --git a/programs/tgetopt.c b/programs/tgetopt.c
index 868600d9..59efcea3 100644
--- a/programs/tgetopt.c
+++ b/programs/tgetopt.c
@@ -70,7 +70,7 @@ tgetopt(int argc, tchar *argv[], const tchar *optstring)
 		} else {
 			/* More short options in previous arg */
 			tchar opt = *nextchar;
-			tchar *p = tstrchr(optstring, opt);
+			const tchar *p = tstrchr(optstring, opt);
 			if (p == NULL) {
 				if (topterr)
 					msg("invalid option -- '%"TC"'", opt);