diff --git a/pyo3-ffi/src/cpython/pystate.rs b/pyo3-ffi/src/cpython/pystate.rs
index 3025abca..232a5165 100644
--- a/pyo3-ffi/src/cpython/pystate.rs
+++ b/pyo3-ffi/src/cpython/pystate.rs
@@ -8,7 +8,7 @@ use std::os::raw::c_int;
 
 // skipped _PyInterpreterState_GetMainModule
 
-pub type Py_tracefunc = extern "C" fn(
+pub type Py_tracefunc = unsafe extern "C" fn(
     obj: *mut PyObject,
     frame: *mut PyFrameObject,
     what: c_int,