diff --git a/.github/workflows/server.yml b/.github/workflows/server.yml
index b7e1289e..85cadf69 100644
--- a/.github/workflows/server.yml
+++ b/.github/workflows/server.yml
@@ -44,10 +44,27 @@ jobs:
             minor=$(python3 --version | cut -d. -f2)
             if [ "$minor" -ge 7 ]; then
               python -m pip install --upgrade "pip==24.0" --only-binary=:all:
+              python -m pip install .
             else
+              # Python 3.6 runs from a checkout (see README), not a pip install.
+              # Just install the runtime deps, pinned per pyproject.toml.
               python -m pip install --upgrade "pip==21.3.1" --only-binary=:all:
+              python -m pip install \
+                "channelfinder @ https://github.com/ChannelFinder/pyCFClient/archive/refs/tags/v3.2.0.zip#sha256=ec89537f336c4cb8db18909c4b02176dd5fbd03f5872a6527129879cbf3f7c85" \
+                "dataclasses==0.8" \
+                "requests==2.27.1" \
+                "twisted==21.7.0"
+            fi
+        - name: Import smoke test
+          run: |
+            minor=$(python3 --version | cut -d. -f2)
+            if [ "$minor" -lt 7 ]; then
+              # Intentional for 3.6: run from the checkout, as documented.
+              PYTHONPATH=. python -c "from twisted.plugins import recceiver_plugin"
+            else
+              # Run outside the checkout so this fails if pip didn't install it.
+              cd /tmp && python -c "from twisted.plugins import recceiver_plugin"
             fi
-            python -m pip install --no-deps .
   test-unit:
     runs-on: ubuntu-latest
     needs: build-server
diff --git a/server/pyproject.toml b/server/pyproject.toml
index f13f8168..6d19a201 100644
--- a/server/pyproject.toml
+++ b/server/pyproject.toml
@@ -30,10 +30,10 @@ dependencies = [
   "channelfinder @ https://github.com/ChannelFinder/pyCFClient/archive/refs/tags/v3.2.0.zip",
   "dataclasses; python_version<'3.7'",
   "requests>=2.27.1,<2.28; python_version<'3.7'",
-  "requests>=2.31,<2.32; python_version<'3.8'",
+  "requests>=2.31,<2.32; python_version>='3.7' and python_version<'3.8'",
   "requests>=2.32.3,<2.33; python_version>='3.8'",
   "twisted>=21.7,<22; python_version<'3.7'",
-  "twisted>=22.10,<23; python_version<'3.8'",
+  "twisted>=22.10,<23; python_version>='3.7' and python_version<'3.8'",
   "twisted>=24.11,<24.12; python_version>='3.8'",
 ]
 optional-dependencies.metrics = [ "prometheus-client" ]
diff --git a/server/recceiver/processors.py b/server/recceiver/processors.py
index d1c32a3e..0dd06794 100644
--- a/server/recceiver/processors.py
+++ b/server/recceiver/processors.py
@@ -5,6 +5,7 @@
 import os
 from configparser import ConfigParser as Parser
 from os.path import expanduser
+from typing import Dict
 
 from twisted.application import service
 from twisted.internet import defer, task
@@ -22,9 +23,9 @@
 ]
 
 
-def _env_vars(section: str) -> dict[str, str]:
+def _env_vars(section: str) -> Dict[str, str]:
     prefix = "RECCEIVER_" + section.upper() + "_"
-    return {k.removeprefix(prefix).lower(): v for k, v in os.environ.items() if k.startswith(prefix)}
+    return {k[len(prefix) :].lower(): v for k, v in os.environ.items() if k.startswith(prefix)}
 
 
 class ConfigAdapter(object):
diff --git a/server/recceiver/recast.py b/server/recceiver/recast.py
index be4af974..ef39fd81 100644
--- a/server/recceiver/recast.py
+++ b/server/recceiver/recast.py
@@ -4,6 +4,7 @@
 import logging
 import random
 import time
+from typing import DefaultDict, Dict, List, Set, Tuple
 
 from twisted.internet import defer, protocol
 from twisted.internet.interfaces import IAddress
@@ -212,11 +213,11 @@ class Transaction:
     connected: bool
     initial: bool
     srcid: int
-    records_to_add: dict[int, tuple[str, str]]
-    client_infos: dict[str, str]
-    record_infos_to_add: dict[int, dict[str, str]]
-    aliases: collections.defaultdict[int, list[str]]
-    records_to_delete: set[int]
+    records_to_add: Dict[int, Tuple[str, str]]
+    client_infos: Dict[str, str]
+    record_infos_to_add: Dict[int, Dict[str, str]]
+    aliases: DefaultDict[int, List[str]]
+    records_to_delete: Set[int]
 
     def __init__(self, ep: IAddress, id: int) -> None:
         self.connected = True