diff --git a/src/platform/nm-netlink.c b/src/platform/nm-netlink.c
index 8e12fad3ce..71506a2c37 100644
--- a/src/platform/nm-netlink.c
+++ b/src/platform/nm-netlink.c
@@ -214,6 +214,8 @@ nlmsg_reserve (struct nl_msg *n, size_t len, int pad)
 	size_t nlmsg_len = n->nm_nlh->nlmsg_len;
 	size_t tlen;
 
+	nm_assert (pad >= 0);
+
 	if (len > n->nm_size)
 		return NULL;
 
@@ -328,10 +330,18 @@ void nlmsg_free (struct nl_msg *msg)
 /*****************************************************************************/
 
 int
-nlmsg_append (struct nl_msg *n, void *data, size_t len, int pad)
+nlmsg_append (struct nl_msg *n,
+              const void *data,
+              size_t len,
+              int pad)
 {
 	void *tmp;
 
+	nm_assert (n);
+	nm_assert (data);
+	nm_assert (len > 0);
+	nm_assert (pad >= 0);
+
 	tmp = nlmsg_reserve (n, len, pad);
 	if (tmp == NULL)
 		return -ENOMEM;
diff --git a/src/platform/nm-netlink.h b/src/platform/nm-netlink.h
index 6d71562d9c..094a3c6fde 100644
--- a/src/platform/nm-netlink.h
+++ b/src/platform/nm-netlink.h
@@ -400,7 +400,13 @@ struct nl_msg *nlmsg_alloc_simple (int nlmsgtype, int flags);
 
 void *nlmsg_reserve (struct nl_msg *n, size_t len, int pad);
 
-int nlmsg_append (struct nl_msg *n, void *data, size_t len, int pad);
+int nlmsg_append (struct nl_msg *n,
+                  const void *data,
+                  size_t len,
+                  int pad);
+
+#define nlmsg_append_struct(n, data) \
+	nlmsg_append (n, (data), sizeof (*(data)), NLMSG_ALIGNTO)
 
 void nlmsg_free (struct nl_msg *msg);