diff --git a/CHANGES/5110.bugfix b/CHANGES/5110.bugfix
new file mode 100644
index 00000000000..14d63a9b8a2
--- /dev/null
+++ b/CHANGES/5110.bugfix
@@ -0,0 +1,3 @@
+Fix a variable-shadowing bug causing `ThreadedResolver.resolve` to
+return the resolved IP as the "hostname" in each record, which prevented
+validation of HTTPS connections.
diff --git a/aiohttp/resolver.py b/aiohttp/resolver.py
index 89821b2dfd1..9e77771f898 100644
--- a/aiohttp/resolver.py
+++ b/aiohttp/resolver.py
@@ -26,10 +26,10 @@ def __init__(self, loop: Optional[asyncio.AbstractEventLoop] = None) -> None:
         self._loop = get_running_loop(loop)
 
     async def resolve(
-        self, host: str, port: int = 0, family: int = socket.AF_INET
+        self, hostname: str, port: int = 0, family: int = socket.AF_INET
     ) -> List[Dict[str, Any]]:
         infos = await self._loop.getaddrinfo(
-            host, port, type=socket.SOCK_STREAM, family=family
+            hostname, port, type=socket.SOCK_STREAM, family=family
         )
 
         hosts = []
@@ -46,7 +46,7 @@ async def resolve(
                 host, port = address[:2]
             hosts.append(
                 {
-                    "hostname": host,
+                    "hostname": hostname,
                     "host": host,
                     "port": port,
                     "family": family,
diff --git a/tests/test_connector.py b/tests/test_connector.py
index 994b82cb2a0..d22c69f2fda 100644
--- a/tests/test_connector.py
+++ b/tests/test_connector.py
@@ -675,10 +675,10 @@ async def test_tcp_connector_resolve_host(loop) -> None:
     for rec in res:
         if rec["family"] == socket.AF_INET:
             assert rec["host"] == "127.0.0.1"
-            assert rec["hostname"] == "127.0.0.1"
+            assert rec["hostname"] == "localhost"
             assert rec["port"] == 8080
         elif rec["family"] == socket.AF_INET6:
-            assert rec["hostname"] == "::1"
+            assert rec["hostname"] == "localhost"
             assert rec["port"] == 8080
             if platform.system() == "Darwin":
                 assert rec["host"] in ("::1", "fe80::1", "fe80::1%lo0")
diff --git a/tests/test_resolver.py b/tests/test_resolver.py
index 3b58b96e2c3..199707e7a42 100644
--- a/tests/test_resolver.py
+++ b/tests/test_resolver.py
@@ -130,6 +130,7 @@ async def test_threaded_resolver_positive_lookup() -> None:
     loop.getaddrinfo = fake_addrinfo(["127.0.0.1"])
     resolver = ThreadedResolver(loop=loop)
     real = await resolver.resolve("www.python.org")
+    assert real[0]["hostname"] == "www.python.org"
     ipaddress.ip_address(real[0]["host"])