diff --git a/lightningd/jsonrpc.c b/lightningd/jsonrpc.c
index 626e1f874..70e3d2423 100644
--- a/lightningd/jsonrpc.c
+++ b/lightningd/jsonrpc.c
@@ -319,6 +319,7 @@ static void connection_complete_error(struct json_connection *jcon,
 
 	assert(id != NULL);
 
+	assert(cmd);
 	if (cmd->ok)
 		*(cmd->ok) = false;