diff --git a/conda_forge_tick/update_prs.py b/conda_forge_tick/update_prs.py
index 2e60c658ec..02812ded1a 100644
--- a/conda_forge_tick/update_prs.py
+++ b/conda_forge_tick/update_prs.py
@@ -23,10 +23,6 @@
 
 # from conda_forge_tick.profiler import profiling
 
-
-if typing.TYPE_CHECKING:
-    from .cli import CLIArgs
-
 logger = logging.getLogger("conda_forge_tick.update_prs")
 
 NUM_GITHUB_THREADS = 2
diff --git a/conda_forge_tick/update_upstream_versions.py b/conda_forge_tick/update_upstream_versions.py
index 9378a0a410..59e0461628 100644
--- a/conda_forge_tick/update_upstream_versions.py
+++ b/conda_forge_tick/update_upstream_versions.py
@@ -9,6 +9,7 @@
     Dict,
     Iterable,
     Iterator,
+    List,
     Literal,
     Mapping,
     Optional,
@@ -65,7 +66,7 @@ def get_latest_version(
     name: str,
     attrs: Mapping[str, Any],
     sources: Iterable[AbstractSource],
-) -> Dict[str, Union[bool, str]]:
+) -> Dict[str, Union[Literal[False], str]]:
     """
     Given a package, return the new version information to be written into the cf-graph.
     :param name: the name of the package.
@@ -87,19 +88,23 @@ def get_latest_version(
         {},
         None,
     )
+
+    sources_to_use: Iterable[AbstractSource]
     if version_sources is not None:
         version_sources = [vs.lower() for vs in version_sources]
-        sources_to_use = []
+        sources_to_use_list = []
         for vs in version_sources:
             for source in sources:
                 if source.name.lower() == vs:
-                    sources_to_use.append(source)
+                    sources_to_use_list.append(source)
                     break
             else:
                 logger.warning(
                     f"Package {name} requests version source '{vs}' which is not available. Skipping.",
                 )
 
+        sources_to_use = sources_to_use_list
+
         logger.debug(
             f"{name} defines the following custom version sources: {[source.name for source in sources_to_use]}",
         )
@@ -215,12 +220,12 @@ def include_node(package_name: str, payload_attrs: Mapping) -> bool:
 
 def _update_upstream_versions_sequential(
     to_update: Iterable[Tuple[str, Mapping]],
-    sources: Iterable[AbstractSource] = None,
+    sources: Iterable[AbstractSource],
 ) -> None:
     node_count = 0
     for node, attrs in to_update:
         # checking each node
-        version_data = {}
+        version_data: Dict[str, Union[Literal[False], str]] = {}
 
         # New version request
         try:
@@ -273,7 +278,7 @@ def _update_upstream_versions_process_pool(
         n_left = len(futures)
         start = time.time()
         # eta :: elapsed time average
-        eta = -1
+        eta = -1.0
         for f in as_completed(futures):
             n_left -= 1
             if n_left % 10 == 0:
@@ -315,7 +320,7 @@ def _update_upstream_versions_process_pool(
 
 def update_upstream_versions(
     gx: nx.DiGraph,
-    sources: Iterable[AbstractSource] = None,
+    sources: Optional[Iterable[AbstractSource]] = None,
     debug: bool = False,
     job=1,
     n_jobs=1,
diff --git a/tests/test_upstream_versions.py b/tests/test_upstream_versions.py
index 36e2e251c7..01e9585e81 100644
--- a/tests/test_upstream_versions.py
+++ b/tests/test_upstream_versions.py
@@ -2,7 +2,7 @@
 import os
 import random
 from concurrent.futures import Future
-from typing import Mapping
+from typing import Dict, Mapping
 from unittest import mock
 from unittest.mock import MagicMock, Mock, patch
 
@@ -1145,7 +1145,7 @@ def test_include_node_parsing_error(caplog):
 
 def test_include_node_no_payload():
     package_name = "testpackage"
-    payload_attrs = {}
+    payload_attrs: Dict = {}
 
     assert include_node(package_name, payload_attrs)
 
@@ -1467,8 +1467,8 @@ def test_update_upstream_versions_process_pool(
         ("testpackage2", {"version": "1.2.4"}),
     ]
 
-    future_1 = Future()
-    future_2 = Future()
+    future_1: Future[Dict[str, str]] = Future()
+    future_2: Future[Dict[str, str]] = Future()
 
     pool_mock = executor_mock.return_value.__enter__.return_value
     pool_mock.submit.side_effect = [future_1, future_2]
@@ -1518,7 +1518,7 @@ def test_update_upstream_versions_process_pool_exception(
         ("testpackage", {"version": "2.2.3"}),
     ]
 
-    future = Future()
+    future: Future[Dict[str, str]] = Future()
 
     pool_mock = executor_mock.return_value.__enter__.return_value
     pool_mock.submit.return_value = future
@@ -1561,7 +1561,7 @@ def test_update_upstream_versions_process_pool_exception_repr_exception(
         ("testpackage", {"version": "2.2.3"}),
     ]
 
-    future = Future()
+    future: Future[Dict[str, str]] = Future()
 
     pool_mock = executor_mock.return_value.__enter__.return_value
     pool_mock.submit.return_value = future