diff --git a/examples/sequential/src/module.rs b/examples/sequential/src/module.rs
index 604bfe393c5..5e71f07a865 100644
--- a/examples/sequential/src/module.rs
+++ b/examples/sequential/src/module.rs
@@ -3,7 +3,7 @@ use pyo3_ffi::*;
 use std::os::raw::{c_int, c_void};
 
 pub static mut MODULE_DEF: PyModuleDef = PyModuleDef {
-    m_base: PyModuleDef_HEAD_INIT(),
+    m_base: PyModuleDef_HEAD_INIT,
     m_name: c_str!("sequential").as_ptr(),
     m_doc: c_str!("A library for generating sequential ids, written in Rust.").as_ptr(),
     m_size: mem::size_of::<sequential_state>() as Py_ssize_t,
diff --git a/examples/string-sum/src/lib.rs b/examples/string-sum/src/lib.rs
index 8929d788caf..ce71ab38f87 100644
--- a/examples/string-sum/src/lib.rs
+++ b/examples/string-sum/src/lib.rs
@@ -4,7 +4,7 @@ use std::ptr;
 use pyo3_ffi::*;
 
 static mut MODULE_DEF: PyModuleDef = PyModuleDef {
-    m_base: PyModuleDef_HEAD_INIT(),
+    m_base: PyModuleDef_HEAD_INIT,
     m_name: c_str!("string_sum").as_ptr(),
     m_doc: c_str!("A Python module written in Rust.").as_ptr(),
     m_size: 0,
diff --git a/pyo3-ffi/README.md b/pyo3-ffi/README.md
index 2f433c62435..200c78cec14 100644
--- a/pyo3-ffi/README.md
+++ b/pyo3-ffi/README.md
@@ -50,7 +50,7 @@ use std::ptr;
 use pyo3_ffi::*;
 
 static mut MODULE_DEF: PyModuleDef = PyModuleDef {
-    m_base: PyModuleDef_HEAD_INIT(),
+    m_base: PyModuleDef_HEAD_INIT,
     m_name: c_str!("string_sum").as_ptr(),
     m_doc: c_str!("A Python module written in Rust.").as_ptr(),
     m_size: 0,
diff --git a/pyo3-ffi/src/lib.rs b/pyo3-ffi/src/lib.rs
index fbc17878211..55c7f31404f 100644
--- a/pyo3-ffi/src/lib.rs
+++ b/pyo3-ffi/src/lib.rs
@@ -88,7 +88,7 @@
 //! use pyo3_ffi::*;
 //!
 //! static mut MODULE_DEF: PyModuleDef = PyModuleDef {
-//!     m_base: PyModuleDef_HEAD_INIT(),
+//!     m_base: PyModuleDef_HEAD_INIT,
 //!     m_name: c_str!("string_sum").as_ptr(),
 //!     m_doc: c_str!("A Python module written in Rust.").as_ptr(),
 //!     m_size: 0,
diff --git a/pyo3-ffi/src/moduleobject.rs b/pyo3-ffi/src/moduleobject.rs
index bf04da660cf..b9026997d2e 100644
--- a/pyo3-ffi/src/moduleobject.rs
+++ b/pyo3-ffi/src/moduleobject.rs
@@ -59,14 +59,12 @@ pub struct PyModuleDef_Base {
     pub m_copy: *mut PyObject,
 }
 
-pub const fn PyModuleDef_HEAD_INIT() -> PyModuleDef_Base {
-    PyModuleDef_Base {
-        ob_base: PyObject_HEAD_INIT(),
-        m_init: None,
-        m_index: 0,
-        m_copy: std::ptr::null_mut(),
-    }
-}
+pub const PyModuleDef_HEAD_INIT: PyModuleDef_Base = PyModuleDef_Base {
+    ob_base: PyObject_HEAD_INIT,
+    m_init: None,
+    m_index: 0,
+    m_copy: std::ptr::null_mut(),
+};
 
 #[repr(C)]
 #[derive(Copy, Clone, Eq, PartialEq)]
diff --git a/pyo3-ffi/src/object.rs b/pyo3-ffi/src/object.rs
index 9baebb8a51f..48aa1f31861 100644
--- a/pyo3-ffi/src/object.rs
+++ b/pyo3-ffi/src/object.rs
@@ -5,7 +5,7 @@ use std::mem;
 use std::os::raw::{c_char, c_int, c_uint, c_ulong, c_void};
 use std::ptr;
 #[cfg(Py_GIL_DISABLED)]
-use std::sync::atomic::{AtomicIsize, AtomicU32, Ordering::Relaxed};
+use std::sync::atomic::{AtomicIsize, AtomicU32, AtomicU8, Ordering::Relaxed};
 
 #[cfg(Py_LIMITED_API)]
 opaque_struct!(PyTypeObject);
@@ -31,33 +31,33 @@ pub const _Py_IMMORTAL_REFCNT_LOCAL: u32 = u32::MAX;
 #[cfg(Py_GIL_DISABLED)]
 pub const _Py_REF_SHARED_SHIFT: isize = 2;
 
-pub const fn PyObject_HEAD_INIT() -> PyObject {
-    PyObject {
-        #[cfg(py_sys_config = "Py_TRACE_REFS")]
-        _ob_next: std::ptr::null_mut(),
-        #[cfg(py_sys_config = "Py_TRACE_REFS")]
-        _ob_prev: std::ptr::null_mut(),
-        #[cfg(Py_GIL_DISABLED)]
-        ob_tid: 0,
-        #[cfg(Py_GIL_DISABLED)]
-        _padding: 0,
-        #[cfg(Py_GIL_DISABLED)]
-        ob_mutex: unsafe { mem::zeroed::<PyMutex>() },
-        #[cfg(Py_GIL_DISABLED)]
-        ob_gc_bits: 0,
-        #[cfg(Py_GIL_DISABLED)]
-        ob_ref_local: AtomicU32::new(_Py_IMMORTAL_REFCNT_LOCAL),
-        #[cfg(Py_GIL_DISABLED)]
-        ob_ref_shared: AtomicIsize::new(0),
-        #[cfg(all(not(Py_GIL_DISABLED), Py_3_12))]
-        ob_refcnt: PyObjectObRefcnt { ob_refcnt: 1 },
-        #[cfg(not(Py_3_12))]
-        ob_refcnt: 1,
-        #[cfg(PyPy)]
-        ob_pypy_link: 0,
-        ob_type: std::ptr::null_mut(),
-    }
-}
+pub const PyObject_HEAD_INIT: PyObject = PyObject {
+    #[cfg(py_sys_config = "Py_TRACE_REFS")]
+    _ob_next: std::ptr::null_mut(),
+    #[cfg(py_sys_config = "Py_TRACE_REFS")]
+    _ob_prev: std::ptr::null_mut(),
+    #[cfg(Py_GIL_DISABLED)]
+    ob_tid: 0,
+    #[cfg(Py_GIL_DISABLED)]
+    _padding: 0,
+    #[cfg(Py_GIL_DISABLED)]
+    ob_mutex: PyMutex {
+        _bits: AtomicU8::new(0),
+    },
+    #[cfg(Py_GIL_DISABLED)]
+    ob_gc_bits: 0,
+    #[cfg(Py_GIL_DISABLED)]
+    ob_ref_local: AtomicU32::new(_Py_IMMORTAL_REFCNT_LOCAL),
+    #[cfg(Py_GIL_DISABLED)]
+    ob_ref_shared: AtomicIsize::new(0),
+    #[cfg(all(not(Py_GIL_DISABLED), Py_3_12))]
+    ob_refcnt: PyObjectObRefcnt { ob_refcnt: 1 },
+    #[cfg(not(Py_3_12))]
+    ob_refcnt: 1,
+    #[cfg(PyPy)]
+    ob_pypy_link: 0,
+    ob_type: std::ptr::null_mut(),
+};
 
 // skipped PyObject_VAR_HEAD
 // skipped Py_INVALID_SIZE
diff --git a/src/impl_/pymodule.rs b/src/impl_/pymodule.rs
index a2325dc07fb..08d55bfa5e8 100644
--- a/src/impl_/pymodule.rs
+++ b/src/impl_/pymodule.rs
@@ -54,8 +54,8 @@ impl ModuleDef {
         doc: &'static CStr,
         initializer: ModuleInitializer,
     ) -> Self {
-        let init = ffi::PyModuleDef {
-            m_base: ffi::PyModuleDef_HEAD_INIT(),
+        const INIT: ffi::PyModuleDef = ffi::PyModuleDef {
+            m_base: ffi::PyModuleDef_HEAD_INIT,
             m_name: std::ptr::null(),
             m_doc: std::ptr::null(),
             m_size: 0,
@@ -69,7 +69,7 @@ impl ModuleDef {
         let ffi_def = UnsafeCell::new(ffi::PyModuleDef {
             m_name: name.as_ptr(),
             m_doc: doc.as_ptr(),
-            ..init
+            ..INIT
         });
 
         ModuleDef {