diff --git a/lib/lwres/include/lwres/netdb.h.in b/lib/lwres/include/lwres/netdb.h.in
index d2aff426ab..ae3f0a4b97 100644
--- a/lib/lwres/include/lwres/netdb.h.in
+++ b/lib/lwres/include/lwres/netdb.h.in
@@ -18,6 +18,7 @@
 #ifndef LWRES_NETDB_H
 #define LWRES_NETDB_H 1
 
+#include <stddef.h>			/* Ensure we have size_t. */
 #include <netdb.h>
 #include <lwres/lang.h>