diff --git a/src/impl_/extract_argument.rs b/src/impl_/extract_argument.rs
index 8a34d7475ca..b2cb91160c6 100644
--- a/src/impl_/extract_argument.rs
+++ b/src/impl_/extract_argument.rs
@@ -48,7 +48,7 @@ where
         obj: &'a Bound<'py, PyAny>,
         holder: &'a mut Option<&'a Bound<'py, T>>,
     ) -> PyResult<Self> {
-        Ok(&*holder.insert(obj.downcast()?))
+        Ok(holder.insert(obj.downcast()?))
     }
 }
 
@@ -261,7 +261,9 @@ impl FunctionDescription {
         );
 
         // Handle positional arguments
-        // Safety: Option<PyArg> has the same memory layout as `*mut ffi::PyObject`
+        // Safety:
+        //  - Option<PyArg> has the same memory layout as `*mut ffi::PyObject`
+        //  - we both have the GIL and can borrow these input references for the `'py` lifetime.
         let args: *const Option<PyArg<'py>> = args.cast();
         let positional_args_provided = nargs as usize;
         let remaining_positional_args = if args.is_null() {
@@ -284,9 +286,12 @@ impl FunctionDescription {
         let mut varkeywords = K::Varkeywords::default();
 
         // Safety: kwnames is known to be a pointer to a tuple, or null
-        let kwnames: &'py Option<Bound<'py, PyTuple>> = std::mem::transmute(&kwnames);
-        if let Some(kwnames) = kwnames.as_ref() {
-            // Safety: &PyAny has the same memory layout as `*mut ffi::PyObject`
+        //  - we both have the GIL and can borrow this input reference for the `'py` lifetime.
+        let kwnames = Borrowed::from_ptr_or_opt(py, kwnames);
+        if let Some(kwnames) = kwnames {
+            // Safety: kwnames is known to be a PyTuple from the Python interpreter
+            let kwnames = kwnames.downcast_unchecked::<PyTuple>();
+            // Safety: PyArg has the same memory layout as `*mut ffi::PyObject`
             let kwargs = ::std::slice::from_raw_parts(
                 (args as *const PyArg<'py>).offset(nargs),
                 kwnames.len(),
@@ -322,7 +327,7 @@ impl FunctionDescription {
     /// - `kwargs` must be a pointer to a PyDict, or NULL.
     pub unsafe fn extract_arguments_tuple_dict<'py, V, K>(
         &self,
-        _py: Python<'py>,
+        py: Python<'py>,
         args: *mut ffi::PyObject,
         kwargs: *mut ffi::PyObject,
         output: &mut [Option<PyArg<'py>>],
@@ -331,11 +336,14 @@ impl FunctionDescription {
         V: VarargsHandler<'py>,
         K: VarkeywordsHandler<'py>,
     {
-        // Safety: Bound has the same layout as a raw pointer, and reference is known to be
-        // borrowed for 'py.
-        let args: &'py Bound<'py, PyTuple> = std::mem::transmute(&args);
-        let kwargs: &'py Option<Bound<'py, PyDict>> = std::mem::transmute(&kwargs);
-        let kwargs = kwargs.as_ref();
+        // Safety:
+        //  - `args` is known to be a tuple
+        //  - `kwargs` is known to be a dict or null
+        //  - we both have the GIL and can borrow these input references for the `'py` lifetime.
+        let args: Borrowed<'py, 'py, PyTuple> =
+            Borrowed::from_ptr(py, args).downcast_unchecked::<PyTuple>();
+        let kwargs: Option<Borrowed<'py, 'py, PyDict>> =
+            Borrowed::from_ptr_or_opt(py, kwargs).map(|kwargs| kwargs.downcast_unchecked());
 
         let num_positional_parameters = self.positional_parameter_names.len();
 
@@ -356,7 +364,7 @@ impl FunctionDescription {
         }
 
         // If any arguments remain, push them to varargs (if possible) or error
-        let varargs = V::handle_varargs_tuple(args, self)?;
+        let varargs = V::handle_varargs_tuple(&args, self)?;
 
         // Handle keyword arguments
         let mut varkeywords = K::Varkeywords::default();
diff --git a/src/types/dict.rs b/src/types/dict.rs
index 2e81662e907..5020e0fb689 100644
--- a/src/types/dict.rs
+++ b/src/types/dict.rs
@@ -517,12 +517,12 @@ impl<'py> PyDictMethods<'py> for Bound<'py, PyDict> {
     }
 }
 
-impl<'py> Bound<'py, PyDict> {
+impl<'a, 'py> Borrowed<'a, 'py, PyDict> {
     /// Iterates over the contents of this dictionary without incrementing reference counts.
     ///
     /// # Safety
     /// It must be known that this dictionary will not be modified during iteration.
-    pub(crate) unsafe fn iter_borrowed<'a>(&'a self) -> BorrowedDictIter<'a, 'py> {
+    pub(crate) unsafe fn iter_borrowed(self) -> BorrowedDictIter<'a, 'py> {
         BorrowedDictIter::new(self)
     }
 }
@@ -672,7 +672,7 @@ mod borrowed_iter {
     /// without incrementing reference counts. This is only safe if it's known
     /// that the dictionary will not be modified during iteration.
     pub struct BorrowedDictIter<'a, 'py> {
-        dict: &'a Bound<'py, PyDict>,
+        dict: Borrowed<'a, 'py, PyDict>,
         ppos: ffi::Py_ssize_t,
         len: ffi::Py_ssize_t,
     }
@@ -710,8 +710,8 @@ mod borrowed_iter {
     }
 
     impl<'a, 'py> BorrowedDictIter<'a, 'py> {
-        pub(super) fn new(dict: &'a Bound<'py, PyDict>) -> Self {
-            let len = dict_len(dict);
+        pub(super) fn new(dict: Borrowed<'a, 'py, PyDict>) -> Self {
+            let len = dict_len(&dict);
             BorrowedDictIter { dict, ppos: 0, len }
         }
     }
diff --git a/src/types/tuple.rs b/src/types/tuple.rs
index e41fcbf0020..e5b0777622e 100644
--- a/src/types/tuple.rs
+++ b/src/types/tuple.rs
@@ -412,7 +412,7 @@ impl<'py> PyTupleMethods<'py> for Bound<'py, PyTuple> {
     }
 
     fn iter_borrowed<'a>(&'a self) -> BorrowedTupleIterator<'a, 'py> {
-        BorrowedTupleIterator::new(self.as_borrowed())
+        self.as_borrowed().iter_borrowed()
     }
 
     fn to_list(&self) -> Bound<'py, PyList> {
@@ -434,6 +434,10 @@ impl<'a, 'py> Borrowed<'a, 'py, PyTuple> {
     unsafe fn get_borrowed_item_unchecked(self, index: usize) -> Borrowed<'a, 'py, PyAny> {
         ffi::PyTuple_GET_ITEM(self.as_ptr(), index as Py_ssize_t).assume_borrowed(self.py())
     }
+
+    pub(crate) fn iter_borrowed(self) -> BorrowedTupleIterator<'a, 'py> {
+        BorrowedTupleIterator::new(self)
+    }
 }
 
 /// Used by `PyTuple::iter()`.