diff --git a/zebra/kernel_null.c b/zebra/kernel_null.c
index 6b96c6d..ec994a6 100644
--- a/zebra/kernel_null.c
+++ b/zebra/kernel_null.c
@@ -9,9 +9,19 @@
 #include "zebra/connected.h"
 
 int kernel_add_ipv4 (struct prefix *a, struct rib *b) { return 0; }
+#ifdef HAVE_SYS_WEAK_ALIAS_PRAGMA
 #pragma weak kernel_delete_ipv4 = kernel_add_ipv4
+#else
+int kernel_delete_ipv4 (struct prefix *a, struct rib *b) { return 0; }
+#endif
+
 int kernel_add_ipv6 (struct prefix *a, struct rib *b) { return 0; }
+#ifdef HAVE_SYS_WEAK_ALIAS_PRAGMA_PRAGMA
 #pragma weak kernel_delete_ipv6 = kernel_add_ipv6
+#else
+int kernel_delete_ipv6 (struct prefix *a, struct rib *b) { return 0; }
+#endif
+
 int kernel_delete_ipv6_old (struct prefix_ipv6 *dest, struct in6_addr *gate,
                             unsigned int index, int flags, int table)
 { return 0; }
@@ -38,4 +48,8 @@
 }
 
 void kernel_init (void) { return; }
+#ifdef HAVE_SYS_WEAK_ALIAS_PRAGMA
 #pragma weak route_read = kernel_init
+#else
+void route_read (void) { return; }
+#endif