Case-sensitive because it's a GNU extension

src/sfxd.c

@@ -326,7 +326,7 @@ void execute_command(struct msg_target tgt, const char *command, const char *par
 
     for (int i = 0; i < sounds_pool.cap; i++) {
       struct sfx_pool_item item = sounds_pool.sounds[i];
-      if (item.key[0] != '\0' && strcasestr(item.key, params)) {
+      if (item.key[0] != '\0' && strstr(item.key, params)) {
         send_txt(tgt, "%s\n", item.key);
       }
     }