diff --git a/modulos/coingecko_api.py b/modulos/coingecko_api.py
index ddf0b71..c75c745 100644
--- a/modulos/coingecko_api.py
+++ b/modulos/coingecko_api.py
@@ -1363,12 +1363,12 @@ def derivatives_exchange_list_with_data(
     if not isinstance(per_page, int):
         raise TypeError('\'per_page\' tem de ser do tipo \'int\'')
     if per_page != -1:
-        api_parameters['per_page'] = per_page
+        api_parameters['per_page'] = str(per_page)
     # page
     if not isinstance(page, int):
         raise TypeError('\'page\' tem de ser do tipo \'int\'')
     if page != -1:
-        api_parameters['page'] = page
+        api_parameters['page'] = str(page)
     
     return API(f'derivatives/exchanges', api_parameters)
 
@@ -1472,7 +1472,7 @@ def nfts_list(
     if not isinstance(page, int):
         raise TypeError('\'page\' tem de ser do tipo \'int\'')
     if page != -1:
-        api_parameters['page'] = page
+        api_parameters['page'] = str(page)
 
     return API(f'nfts/list', api_parameters)