https://github.com/termux/termux-packages/issues/16191

--- a/mu/mu-cmd-server.cc
+++ b/mu/mu-cmd-server.cc
@@ -77,7 +77,7 @@
 	if (tty) // for testing.
 		::printf("[%x]", num);
 	else
-		::printf(COOKIE_PRE "%x" COOKIE_POST, num);
+		::printf("%s%x%s", COOKIE_PRE, num, COOKIE_POST);
 }
 
 static void
