diff --git a/lib/dns/dnsrps.c b/lib/dns/dnsrps.c
index f9e2793a29..d9368140e1 100644
--- a/lib/dns/dnsrps.c
+++ b/lib/dns/dnsrps.c
@@ -16,6 +16,8 @@
 
 #ifdef USE_DNSRPS
 
+#include <stdlib.h>
+
 #include <isc/mem.h>
 #include <isc/string.h>
 #include <isc/util.h>