diff --git a/compat/getopt.c b/compat/getopt.c
index 41a641f7c8..72110a95dd 100644
--- a/compat/getopt.c
+++ b/compat/getopt.c
@@ -38,7 +38,7 @@ static int optind = 1;
 static int optopt;
 static char *optarg;
 
-static int getopt(int argc, char *argv[], char *opts)
+static int getopt(int argc, char *argv[], const char *opts)
 {
     static int sp = 1;
     int c;