diff --git a/src/pricehist/isocurrencies.py b/src/pricehist/isocurrencies.py
index f7079c4..fe02678 100644
--- a/src/pricehist/isocurrencies.py
+++ b/src/pricehist/isocurrencies.py
@@ -25,6 +25,7 @@ Functions:
 
 from dataclasses import dataclass, field
 from importlib.resources import read_binary
+from typing import List
 
 from lxml import etree
 
@@ -36,7 +37,7 @@ class ISOCurrency:
     minor_units: int = None
     name: str = None
     is_fund: bool = False
-    countries: list[str] = field(default_factory=list)
+    countries: List[str] = field(default_factory=list)
     historical: bool = False
     withdrawal_date: str = None
 
diff --git a/src/pricehist/series.py b/src/pricehist/series.py
index d063b90..88a1de3 100644
--- a/src/pricehist/series.py
+++ b/src/pricehist/series.py
@@ -1,5 +1,6 @@
 from dataclasses import dataclass, field, replace
 from decimal import Decimal, getcontext
+from typing import List
 
 from pricehist.price import Price
 
@@ -11,7 +12,7 @@ class Series:
     type: str
     start: str
     end: str
-    prices: list[Price] = field(default_factory=list)
+    prices: List[Price] = field(default_factory=list)
 
     def invert(self):
         return replace(
diff --git a/src/pricehist/sources/alphavantage.py b/src/pricehist/sources/alphavantage.py
index d0eac8c..75cda5d 100644
--- a/src/pricehist/sources/alphavantage.py
+++ b/src/pricehist/sources/alphavantage.py
@@ -5,6 +5,7 @@ import logging
 import os
 from datetime import datetime, timedelta
 from decimal import Decimal
+from typing import List, Tuple
 
 import requests
 
@@ -334,15 +335,15 @@ class AlphaVantage(BaseSource):
             if "Error Message" in data and "apikey " in data["Error Message"]:
                 raise exceptions.CredentialsError([self.API_KEY_NAME], self)
 
-    def _physical_symbols(self) -> list[(str, str)]:
+    def _physical_symbols(self) -> List[Tuple[str, str]]:
         url = "https://www.alphavantage.co/physical_currency_list/"
         return self._get_symbols(url, "Physical: ")
 
-    def _digital_symbols(self) -> list[(str, str)]:
+    def _digital_symbols(self) -> List[Tuple[str, str]]:
         url = "https://www.alphavantage.co/digital_currency_list/"
         return self._get_symbols(url, "Digital: ")
 
-    def _get_symbols(self, url, prefix) -> list[(str, str)]:
+    def _get_symbols(self, url, prefix) -> List[Tuple[str, str]]:
         try:
             response = self.log_curl(requests.get(url))
         except Exception as e:
diff --git a/src/pricehist/sources/basesource.py b/src/pricehist/sources/basesource.py
index 4273678..cab423f 100644
--- a/src/pricehist/sources/basesource.py
+++ b/src/pricehist/sources/basesource.py
@@ -1,6 +1,7 @@
 import logging
 from abc import ABC, abstractmethod
 from textwrap import TextWrapper
+from typing import List, Tuple
 
 import curlify
 
@@ -30,7 +31,7 @@ class BaseSource(ABC):
         pass  # pragma: nocover
 
     @abstractmethod
-    def types(self) -> list[str]:
+    def types(self) -> List[str]:
         pass  # pragma: nocover
 
     @abstractmethod
@@ -41,10 +42,10 @@ class BaseSource(ABC):
         return str.upper()
 
     @abstractmethod
-    def symbols(self) -> list[(str, str)]:
+    def symbols(self) -> List[Tuple[str, str]]:
         pass  # pragma: nocover
 
-    def search(self, query) -> list[(str, str)]:
+    def search(self, query) -> List[Tuple[str, str]]:
         pass  # pragma: nocover
 
     @abstractmethod
diff --git a/tests/pricehist/sources/test_basesource.py b/tests/pricehist/sources/test_basesource.py
index cfd5e80..478d5c2 100644
--- a/tests/pricehist/sources/test_basesource.py
+++ b/tests/pricehist/sources/test_basesource.py
@@ -1,4 +1,5 @@
 import logging
+from typing import List, Tuple
 
 import pytest
 
@@ -22,13 +23,13 @@ class TestSource(BaseSource):
     def start(self) -> str:
         return ""
 
-    def types(self) -> list[str]:
+    def types(self) -> List[str]:
         return []
 
     def notes(self) -> str:
         return ""
 
-    def symbols(self) -> list[(str, str)]:
+    def symbols(self) -> List[Tuple[str, str]]:
         return []
 
     def fetch(self, series: Series) -> Series: