diff --git a/python/src/deltachat/account.py b/python/src/deltachat/account.py
index af2710bed..ddffcdfc1 100644
--- a/python/src/deltachat/account.py
+++ b/python/src/deltachat/account.py
@@ -184,14 +184,18 @@ class Account(object):
         return list(iter_array(dc_array, lambda x: Contact(self._dc_context, x)))
 
     def create_chat_by_contact(self, contact):
-        """ create or get an existing 1:1 chat object for the specified contact.
+        """ create or get an existing 1:1 chat object for the specified contact or contact id.
 
         :param contact: chat_id (int) or contact object.
         :returns: a :class:`deltachat.chatting.Chat` object.
         """
-        assert contact._dc_context == self._dc_context
-        contact_id = getattr(contact, "id", contact)
-        assert isinstance(contact_id, int)
+        if hasattr(contact, "id"):
+            if contact._dc_context != self._dc_context:
+                raise ValueError("Contact belongs to a different Account")
+            contact_id = getattr(contact, "id", contact)
+        else:
+            assert isinstance(contact, int)
+            contact_id = contact
         chat_id = lib.dc_create_chat_by_contact_id(
                         self._dc_context, contact_id)
         return Chat(self._dc_context, chat_id)
@@ -203,6 +207,8 @@ class Account(object):
         :param message: messsage id or message instance.
         :returns: a :class:`deltachat.chatting.Chat` object.
         """
+        if self._dc_context != message._dc_context:
+            raise ValueError("Message belongs to a different Account")
         msg_id = getattr(message, "id", message)
         assert isinstance(msg_id, int)
         chat_id = lib.dc_create_chat_by_msg_id(self._dc_context, msg_id)
diff --git a/python/tests/test_account.py b/python/tests/test_account.py
index d361029ff..e35fbe4f5 100644
--- a/python/tests/test_account.py
+++ b/python/tests/test_account.py
@@ -180,6 +180,17 @@ class TestOfflineAccount:
         assert msg.filename.endswith(msg.basename)
         assert msg.filemime == typeout
 
+    def test_create_chat_mismatch(self, acfactory):
+        ac1 = acfactory.get_configured_offline_account()
+        ac2 = acfactory.get_configured_offline_account()
+        contact1 = ac1.create_contact("some1@hello.com", name="some1")
+        with pytest.raises(ValueError):
+            ac2.create_chat_by_contact(contact1)
+        chat1 = ac1.create_chat_by_contact(contact1)
+        msg = chat1.send_text("hello")
+        with pytest.raises(ValueError):
+            ac2.create_chat_by_message(msg)
+
     def test_chat_message_distinctions(self, acfactory):
         ac1 = acfactory.get_configured_offline_account()
         contact1 = ac1.create_contact("some1@hello.com", name="some1")
diff --git a/src/dc_imex.rs b/src/dc_imex.rs
index 53c36d9d0..49c11ca0f 100644
--- a/src/dc_imex.rs
+++ b/src/dc_imex.rs
@@ -1086,12 +1086,12 @@ unsafe fn export_backup(context: &Context, dir: *const libc::c_char) -> libc::c_
     );
     context.sql.close(&context);
     closed = 1i32;
-    dc_log_info(
-        context,
-        0i32,
-        b"Backup \"%s\" to \"%s\".\x00" as *const u8 as *const libc::c_char,
-        context.get_dbfile(),
-        dest_pathNfilename,
+    info!(
+        context, 
+        0,
+        "Backup \"{}\" to \"{}\".", 
+        as_str(context.get_dbfile()),
+        as_str(dest_pathNfilename),
     );
     if !(0 == dc_copy_file(context, context.get_dbfile(), dest_pathNfilename)) {
         context.sql.open(&context, as_path(context.get_dbfile()), 0);
@@ -1139,13 +1139,11 @@ unsafe fn export_backup(context: &Context, dir: *const libc::c_char) -> libc::c_
                             // scan directory, pass 2: copy files
                             let dir_handle = std::fs::read_dir(dir);
                             if dir_handle.is_err() {
-                                dc_log_error(
+                                error!(
                                     context,
-                                    0i32,
-                                    b"Backup: Cannot copy from blob-directory \"%s\".\x00"
-                                        as *const u8
-                                        as *const libc::c_char,
-                                    context.get_blobdir(),
+                                    0,
+                                    "Backup: Cannot copy from blob-directory \"{}\".",
+                                    as_str(context.get_blobdir()),
                                 );
                             } else {
                                 let dir_handle = dir_handle.unwrap();
@@ -1193,7 +1191,6 @@ unsafe fn export_backup(context: &Context, dir: *const libc::c_char) -> libc::c_
                                         let name_f = entry.file_name();
                                         let name = name_f.to_string_lossy();
                                         if name.starts_with("delt-chat") && name.ends_with(".bak") {
-                                            // dc_log_info(context, 0, "Backup: Skipping \"%s\".", name);
                                             continue;
                                         } else {
                                             info!(context, 0, "EXPORTing filename={}", name);
@@ -1249,13 +1246,7 @@ unsafe fn export_backup(context: &Context, dir: *const libc::c_char) -> libc::c_
                                 }
                             }
                         } else {
-                            dc_log_info(
-                                context,
-                                0i32,
-                                b"Backup: No files to copy.\x00" as *const u8
-                                    as *const libc::c_char,
-                                context.get_blobdir(),
-                            );
+                            info!(context, 0, "Backup: No files to copy.");
                             current_block = 2631791190359682872;
                         }
                         match current_block {