diff --git a/src/httpcore2/httpcore2/_async/http11.py b/src/httpcore2/httpcore2/_async/http11.py
index 769825d9..1248bbff 100644
--- a/src/httpcore2/httpcore2/_async/http11.py
+++ b/src/httpcore2/httpcore2/_async/http11.py
@@ -251,7 +251,10 @@ def is_available(self) -> bool:
 
     def has_expired(self) -> bool:
         now = time.monotonic()
-        keepalive_expired = self._expire_at is not None and now > self._expire_at
+        # Read `_expire_at` once into a local: on free-threaded builds another
+        # thread may reset it to `None` between the check and the comparison.
+        expire_at = self._expire_at
+        keepalive_expired = expire_at is not None and now > expire_at
 
         # If the HTTP connection is idle but the socket is readable, then the
         # only valid state is that the socket is about to return b"", indicating
diff --git a/src/httpcore2/httpcore2/_async/http2.py b/src/httpcore2/httpcore2/_async/http2.py
index 2c143e07..af5b911a 100644
--- a/src/httpcore2/httpcore2/_async/http2.py
+++ b/src/httpcore2/httpcore2/_async/http2.py
@@ -484,7 +484,10 @@ def is_available(self) -> bool:
 
     def has_expired(self) -> bool:
         now = time.monotonic()
-        return self._expire_at is not None and now > self._expire_at
+        # Read `_expire_at` once into a local: on free-threaded builds another
+        # thread may reset it to `None` between the check and the comparison.
+        expire_at = self._expire_at
+        return expire_at is not None and now > expire_at
 
     def is_idle(self) -> bool:
         return self._state == HTTPConnectionState.IDLE
diff --git a/src/httpcore2/httpcore2/_sync/http11.py b/src/httpcore2/httpcore2/_sync/http11.py
index 14d674ae..3d6b9d19 100644
--- a/src/httpcore2/httpcore2/_sync/http11.py
+++ b/src/httpcore2/httpcore2/_sync/http11.py
@@ -251,7 +251,10 @@ def is_available(self) -> bool:
 
     def has_expired(self) -> bool:
         now = time.monotonic()
-        keepalive_expired = self._expire_at is not None and now > self._expire_at
+        # Read `_expire_at` once into a local: on free-threaded builds another
+        # thread may reset it to `None` between the check and the comparison.
+        expire_at = self._expire_at
+        keepalive_expired = expire_at is not None and now > expire_at
 
         # If the HTTP connection is idle but the socket is readable, then the
         # only valid state is that the socket is about to return b"", indicating
diff --git a/src/httpcore2/httpcore2/_sync/http2.py b/src/httpcore2/httpcore2/_sync/http2.py
index 6daf0ac8..457d2a8b 100644
--- a/src/httpcore2/httpcore2/_sync/http2.py
+++ b/src/httpcore2/httpcore2/_sync/http2.py
@@ -484,7 +484,10 @@ def is_available(self) -> bool:
 
     def has_expired(self) -> bool:
         now = time.monotonic()
-        return self._expire_at is not None and now > self._expire_at
+        # Read `_expire_at` once into a local: on free-threaded builds another
+        # thread may reset it to `None` between the check and the comparison.
+        expire_at = self._expire_at
+        return expire_at is not None and now > expire_at
 
     def is_idle(self) -> bool:
         return self._state == HTTPConnectionState.IDLE