diff --git a/google/cloud/sql/connector/instance.py b/google/cloud/sql/connector/instance.py
index 7e6ed5a7..2490ce61 100644
--- a/google/cloud/sql/connector/instance.py
+++ b/google/cloud/sql/connector/instance.py
@@ -104,11 +104,13 @@ async def force_refresh(self) -> None:
         """
         # if next refresh is not already in progress, cancel it and schedule new one immediately
         if not self._lock.locked():
-            self._next.cancel()
-            self._next = self._schedule_refresh(0)
+            async with self._lock:
+                self._next.cancel()
+                self._next = self._schedule_refresh(0)
         # block all sequential connection attempts on the next refresh result if current is invalid
-        if not await _is_valid(self._current):
-            self._current = self._next
+        async with self._lock:
+            if not await _is_valid(self._current):
+                self._current = self._next
 
     async def _perform_refresh(self) -> ConnectionInfo:
         """Retrieves instance metadata and ephemeral certificate from the
@@ -122,8 +124,8 @@ async def _perform_refresh(self) -> ConnectionInfo:
         """
         async with self._lock:
             logger.debug(
-                f"['{self._instance_connection_string}']: Connection info refresh "
-                "operation started"
+                f"['{self._instance_connection_string}']: Connection info "
+                "refresh operation started"
             )
 
             try:
@@ -241,8 +243,9 @@ async def close(self) -> None:
             f"['{self._instance_connection_string}']: Canceling connection info "
             "refresh operation tasks"
         )
-        self._current.cancel()
-        self._next.cancel()
-        # gracefully wait for tasks to cancel
-        tasks = asyncio.gather(self._current, self._next, return_exceptions=True)
+        async with self._lock:
+            self._current.cancel()
+            self._next.cancel()
+            # gracefully wait for tasks to cancel
+            tasks = asyncio.gather(self._current, self._next, return_exceptions=True)
         await asyncio.wait_for(tasks, timeout=2.0)