diff --git a/telethon/helpers.py b/telethon/helpers.py
index 6c782b0b..96ef8135 100644
--- a/telethon/helpers.py
+++ b/telethon/helpers.py
@@ -40,7 +40,7 @@ def add_surrogate(text):
         # SMP -> Surrogate Pairs (Telegram offsets are calculated with these).
         # See https://en.wikipedia.org/wiki/Plane_(Unicode)#Overview for more.
         ''.join(chr(y) for y in struct.unpack('<HH', x.encode('utf-16le')))
-        if (0x10000 <= ord(x) <= 0x10FFFF) else x for x in text
+        if (0x10000 <= ord(x) <= 0x10FFFF) else x for x in str(text)
     )