diff --git a/python/src/deltachat/message.py b/python/src/deltachat/message.py
index 745893f40..bfd5a95b1 100644
--- a/python/src/deltachat/message.py
+++ b/python/src/deltachat/message.py
@@ -110,7 +110,13 @@ class Message(object):
 
     def continue_key_transfer(self, setup_code):
         """ extract key and use it as primary key for this account. """
-        lib.dc_continue_key_transfer(self._dc_context, self.id, as_dc_charpointer(setup_code))
+        res = lib.dc_continue_key_transfer(
+                self._dc_context,
+                self.id,
+                as_dc_charpointer(setup_code)
+        )
+        if res == 0:
+            raise ValueError("could not decrypt")
 
     @props.with_doc
     def time_sent(self):
diff --git a/python/tests/test_account.py b/python/tests/test_account.py
index c0090d27e..43963d9aa 100644
--- a/python/tests/test_account.py
+++ b/python/tests/test_account.py
@@ -537,6 +537,9 @@ class TestOnlineAccount:
         ev = ac2._evlogger.get_matching("DC_EVENT_INCOMING_MSG|DC_EVENT_MSGS_CHANGED")
         msg = ac2.get_message_by_id(ev[2])
         assert msg.is_setup_message()
+        # first try a bad setup code
+        with pytest.raises(ValueError):
+            msg.continue_key_transfer(str(reversed(setup_code)))
         print("*************** Incoming ASM File at: ", msg.filename)
         print("*************** Setup Code: ", setup_code)
         msg.continue_key_transfer(setup_code)
diff --git a/src/pgp.rs b/src/pgp.rs
index 3aa018d68..2a86504b1 100644
--- a/src/pgp.rs
+++ b/src/pgp.rs
@@ -289,10 +289,11 @@ pub fn dc_pgp_symm_decrypt(passphrase: &str, ctext: &[u8]) -> Option<Vec<u8>> {
 
     enc_msg
         .and_then(|msg| {
-            let mut decryptor = msg
-                .decrypt_with_password(|| passphrase.into())
-                .expect("failed decryption");
-            decryptor.next().expect("no message")
+            let mut decryptor = msg.decrypt_with_password(|| passphrase.into())?;
+            match decryptor.next() {
+                Some(x) => x,
+                None => Err(pgp::errors::Error::InvalidInput),
+            }
         })
         .and_then(|msg| msg.get_content())
         .ok()