diff --git a/lib/bootconfig.c b/lib/bootconfig.c
index 2ed9ee3dc81c..926094d97397 100644
--- a/lib/bootconfig.c
+++ b/lib/bootconfig.c
@@ -440,6 +440,17 @@ int __init xbc_snprint_cmdline(char *buf, size_t size, struct xbc_node *root)
 	 * itself is well defined and returns the would-be length.
 	 */
 	xbc_node_for_each_key_value(root, knode, val) {
+		/*
+		 * An empty or value-only @root (e.g. "kernel {}" or
+		 * "kernel = x", possibly alongside "kernel.foo = bar")
+		 * yields @root itself here. Skip it: composing a key for it
+		 * would fail with -EINVAL, yet any real descendant keys must
+		 * still be rendered. An entirely empty subtree then renders
+		 * nothing and returns 0 rather than an error.
+		 */
+		if (knode == root)
+			continue;
+
 		ret = xbc_node_compose_key_after(root, knode,
 					xbc_namebuf, XBC_KEYLEN_MAX);
 		if (ret < 0)