diff --git a/telethon/tl/entity_database.py b/telethon/tl/entity_database.py
index 00284409..a9f6332a 100644
--- a/telethon/tl/entity_database.py
+++ b/telethon/tl/entity_database.py
@@ -177,8 +177,10 @@ class EntityDatabase:
 
     def get_input_entity(self, peer):
         try:
-            i, k = utils.get_peer_id(peer, add_mark=True, get_kind=True)
-            h = self._input_entities[i]
+            i = utils.get_peer_id(peer, add_mark=True)
+            h = self._input_entities[i]  # we store the IDs marked
+            i, k = utils.resolve_id(i)  # removes the mark and returns kind
+
             if k == PeerUser:
                 return InputPeerUser(i, h)
             elif k == PeerChat:
diff --git a/telethon/utils.py b/telethon/utils.py
index 9efc5ee5..3fa84155 100644
--- a/telethon/utils.py
+++ b/telethon/utils.py
@@ -303,16 +303,14 @@ def get_input_media(media, user_caption=None, is_photo=False):
     _raise_cast_fail(media, 'InputMedia')
 
 
-def get_peer_id(peer, add_mark=False, get_kind=False):
+def get_peer_id(peer, add_mark=False):
     """Finds the ID of the given peer, and optionally converts it to
        the "bot api" format if 'add_mark' is set to True.
-
-       If 'get_kind', the kind will be returned as a second value.
     """
     # First we assert it's a Peer TLObject, or early return for integers
     if not isinstance(peer, TLObject):
         if isinstance(peer, int):
-            return (peer, PeerUser) if get_kind else peer
+            return peer
         else:
             _raise_cast_fail(peer, 'int')
 
@@ -321,25 +319,20 @@ def get_peer_id(peer, add_mark=False, get_kind=False):
         peer = get_input_peer(peer, allow_self=False)
 
     # Set the right ID/kind, or raise if the TLObject is not recognised
-    i, k = None, None
     if isinstance(peer, PeerUser) or isinstance(peer, InputPeerUser):
-        i, k = peer.user_id, PeerUser
+        return peer.user_id
     elif isinstance(peer, PeerChat) or isinstance(peer, InputPeerChat):
-        i, k = peer.chat_id, PeerChat
+        return -peer.chat_id if add_mark else peer.chat_id
     elif isinstance(peer, PeerChannel) or isinstance(peer, InputPeerChannel):
-        i, k = peer.channel_id, PeerChannel
-    else:
-        _raise_cast_fail(peer, 'int')
-
-    if add_mark:
-        if k == PeerChat:
-            i = -i
-        elif k == PeerChannel:
+        i = peer.channel_id
+        if add_mark:
             # Concat -100 through math tricks, .to_supergroup() on Madeline
             # IDs will be strictly positive -> log works
-            i = -(i + pow(10, math.floor(math.log10(i) + 3)))
+            return -(i + pow(10, math.floor(math.log10(i) + 3)))
+        else:
+            return i
 
-    return (i, k) if get_kind else i  # return kind only if get_kind
+    _raise_cast_fail(peer, 'int')
 
 
 def resolve_id(marked_id):