diff --git a/lib/dns/time.c b/lib/dns/time.c
index d331ca3bfe..b3d2c2d084 100644
--- a/lib/dns/time.c
+++ b/lib/dns/time.c
@@ -35,7 +35,7 @@
 #include <dns/result.h>
 #include <dns/time.h>
 
-static int days[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+static const int days[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
 
 isc_result_t
 dns_time64_totext(isc_int64_t t, isc_buffer_t *target) {