diff --git a/telebot/apihelper.py b/telebot/apihelper.py
index ff8c8e231..fc76a0016 100644
--- a/telebot/apihelper.py
+++ b/telebot/apihelper.py
@@ -1658,7 +1658,7 @@ def create_invoice_link(token, title, description, payload, provider_token,
         payload['send_phone_number_to_provider'] = send_phone_number_to_provider
     if send_email_to_provider:
         payload['send_email_to_provider'] = send_email_to_provider
-    if is_flexible:
+    if is_flexible is not None:
         payload['is_flexible'] = is_flexible
     return _make_request(token, method_url, params=payload, method='post')
 
diff --git a/telebot/asyncio_helper.py b/telebot/asyncio_helper.py
index 51b60e98f..1c01893bd 100644
--- a/telebot/asyncio_helper.py
+++ b/telebot/asyncio_helper.py
@@ -1636,7 +1636,7 @@ async def create_invoice_link(token, title, description, payload, provider_token
         payload['send_phone_number_to_provider'] = send_phone_number_to_provider
     if send_email_to_provider:
         payload['send_email_to_provider'] = send_email_to_provider
-    if is_flexible:
+    if is_flexible is not None:
         payload['is_flexible'] = is_flexible
     return await _process_request(token, method_url, params=payload, method='post')