--- proftpd-1.3.9/src/encode.c.old	2025-05-14 21:20:14.462515453 -0400
+++ proftpd-1.3.9/src/encode.c	2025-05-14 21:23:59.252180669 -0400
@@ -67,6 +67,8 @@
     defined(DARWIN11) || defined(DARWIN12)
 
     nconv = iconv(conv, (char **) &inbuf, inbuflen, &outbuf, outbuflen);
+#elif defined(__illumos__)
+    nconv = iconv(conv, (char ** restrict) &inbuf, inbuflen, &outbuf, outbuflen);
 #else
     nconv = iconv(conv, &inbuf, inbuflen, &outbuf, outbuflen);
 #endif