diff --git a/monkey/monkey_island/cc/server_utils/encryption/encryption_key_types.py b/monkey/monkey_island/cc/server_utils/encryption/encryption_key_types.py
index 5fcc41f0b..65872ca5a 100644
--- a/monkey/monkey_island/cc/server_utils/encryption/encryption_key_types.py
+++ b/monkey/monkey_island/cc/server_utils/encryption/encryption_key_types.py
@@ -1,6 +1,8 @@
 class EncryptionKey32Bytes(bytes):
     def __init__(self, key: bytes):
+        if not isinstance(key, bytes):
+            raise TypeError("Key is not of type `bytes`")
         if len(key) == 32:
             self.key = key
         else:
-            raise ValueError("Key size should be 32 bytes.")
+            raise ValueError("Key size should be 32 bytes")