diff --git a/gridfs/asynchronous/grid_file.py b/gridfs/asynchronous/grid_file.py
index 4d6140750e..afc1a0f756 100644
--- a/gridfs/asynchronous/grid_file.py
+++ b/gridfs/asynchronous/grid_file.py
@@ -1176,20 +1176,22 @@ def __getattr__(self, name: str) -> Any:
         raise AttributeError("GridIn object has no attribute '%s'" % name)
 
     def __setattr__(self, name: str, value: Any) -> None:
-        if _IS_SYNC:
-            # For properties of this instance like _buffer, or descriptors set on
-            # the class like filename, use regular __setattr__
-            if name in self.__dict__ or name in self.__class__.__dict__:
-                object.__setattr__(self, name, value)
-            else:
+        # For properties of this instance like _buffer, or descriptors set on
+        # the class like filename, use regular __setattr__
+        if name in self.__dict__ or name in self.__class__.__dict__:
+            object.__setattr__(self, name, value)
+        else:
+            if _IS_SYNC:
                 # All other attributes are part of the document in db.fs.files.
                 # Store them to be sent to server on close() or if closed, send
                 # them now.
                 self._file[name] = value
                 if self._closed:
                     self._coll.files.update_one({"_id": self._file["_id"]}, {"$set": {name: value}})
-        else:
-            object.__setattr__(self, name, value)
+            else:
+                raise AttributeError(
+                    "AsyncGridIn does not support __setattr__. Use AsyncGridIn.set() instead"
+                )
 
     async def set(self, name: str, value: Any) -> None:
         # For properties of this instance like _buffer, or descriptors set on
@@ -1484,6 +1486,17 @@ def __init__(
     _file: Any
     _chunk_iter: Any
 
+    async def __anext__(self) -> bytes:
+        return super().__next__()
+
+    def __next__(self) -> bytes:  # noqa: F811, RUF100
+        if _IS_SYNC:
+            return super().__next__()
+        else:
+            raise TypeError(
+                "AsyncGridOut does not support synchronous iteration. Use `async for` instead"
+            )
+
     async def open(self) -> None:
         if not self._file:
             _disallow_transactions(self._session)
@@ -1511,6 +1524,7 @@ async def readchunk(self) -> bytes:
         """Reads a chunk at a time. If the current position is within a
         chunk the remainder of the chunk is returned.
         """
+        await self.open()
         received = len(self._buffer) - self._buffer_pos
         chunk_data = EMPTY
         chunk_size = int(self.chunk_size)
diff --git a/gridfs/synchronous/grid_file.py b/gridfs/synchronous/grid_file.py
index bc2e29a61d..80015f96e7 100644
--- a/gridfs/synchronous/grid_file.py
+++ b/gridfs/synchronous/grid_file.py
@@ -1166,20 +1166,22 @@ def __getattr__(self, name: str) -> Any:
         raise AttributeError("GridIn object has no attribute '%s'" % name)
 
     def __setattr__(self, name: str, value: Any) -> None:
-        if _IS_SYNC:
-            # For properties of this instance like _buffer, or descriptors set on
-            # the class like filename, use regular __setattr__
-            if name in self.__dict__ or name in self.__class__.__dict__:
-                object.__setattr__(self, name, value)
-            else:
+        # For properties of this instance like _buffer, or descriptors set on
+        # the class like filename, use regular __setattr__
+        if name in self.__dict__ or name in self.__class__.__dict__:
+            object.__setattr__(self, name, value)
+        else:
+            if _IS_SYNC:
                 # All other attributes are part of the document in db.fs.files.
                 # Store them to be sent to server on close() or if closed, send
                 # them now.
                 self._file[name] = value
                 if self._closed:
                     self._coll.files.update_one({"_id": self._file["_id"]}, {"$set": {name: value}})
-        else:
-            object.__setattr__(self, name, value)
+            else:
+                raise AttributeError(
+                    "GridIn does not support __setattr__. Use GridIn.set() instead"
+                )
 
     def set(self, name: str, value: Any) -> None:
         # For properties of this instance like _buffer, or descriptors set on
@@ -1472,6 +1474,15 @@ def __init__(
     _file: Any
     _chunk_iter: Any
 
+    def __next__(self) -> bytes:
+        return super().__next__()
+
+    def __next__(self) -> bytes:  # noqa: F811, RUF100
+        if _IS_SYNC:
+            return super().__next__()
+        else:
+            raise TypeError("GridOut does not support synchronous iteration. Use `for` instead")
+
     def open(self) -> None:
         if not self._file:
             _disallow_transactions(self._session)
@@ -1499,6 +1510,7 @@ def readchunk(self) -> bytes:
         """Reads a chunk at a time. If the current position is within a
         chunk the remainder of the chunk is returned.
         """
+        self.open()
         received = len(self._buffer) - self._buffer_pos
         chunk_data = EMPTY
         chunk_size = int(self.chunk_size)
diff --git a/pyproject.toml b/pyproject.toml
index 4380b57e8d..8452bfe956 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -126,7 +126,7 @@ module = ["service_identity.*"]
 ignore_missing_imports = true
 
 [[tool.mypy.overrides]]
-module = ["pymongo.synchronous.*", "gridfs.synchronous.*"]
+module = ["pymongo.synchronous.*"]
 warn_unused_ignores = false
 disable_error_code = ["unused-coroutine"]
 
@@ -134,6 +134,10 @@ disable_error_code = ["unused-coroutine"]
 module = ["pymongo.asynchronous.*"]
 warn_unused_ignores = false
 
+[[tool.mypy.overrides]]
+module = ["gridfs.synchronous.*"]
+warn_unused_ignores = false
+disable_error_code = ["unused-coroutine", "no-redef"]
 
 [tool.ruff]
 target-version = "py37"