https://sources.debian.org/patches/lsh-utils/2.1-12/missing_include.patch/
--- src/io_commands.c.orig
+++ src/io_commands.c
@@ -36,6 +36,7 @@
 #include "command.h"
 #include "connection.h"
 /* For lsh_get_cstring */
+#include "lsh_string.h"
 #include "format.h"
 #include "io.h"
 #include "queue.h"