diff --git a/src/cipher_analytical_machine/cli.clj b/src/cipher_analytical_machine/cli.clj
index a201c9e..86c05eb 100644
--- a/src/cipher_analytical_machine/cli.clj
+++ b/src/cipher_analytical_machine/cli.clj
@@ -69,6 +69,12 @@
       (map-has-keys? options [:message, :message-file])
       {:exit-message (error-msg ["You can't use message and message-file options at the same time!!!"])}
 
+      (file/is-file-not-exists? (:message-file options))
+      {:exit-message (error-msg ["Please, check the path to the message file!!!"])}
+
+      (file/is-file-exists? (:output-file options))
+      {:exit-message (error-msg ["Please, choose another file!!! Overwriting was prevented!!!"])}
+
       (and (map-has-keys? options [:cipher, :key])
            (or (contains? options :message)
                (contains? options :message-file))