diff --git a/Cython/Runtime/refnanny.pyx b/Cython/Runtime/refnanny.pyx
index a80ec988052..8a76cb9ad10 100644
--- a/Cython/Runtime/refnanny.pyx
+++ b/Cython/Runtime/refnanny.pyx
@@ -50,14 +50,20 @@ cdef extern from *:
 loglevel = 0
 reflog = []
 
-cdef log(level, action, obj, lineno):
-    if reflog is None:
-        # can happen during finalisation
-        return
-    if loglevel >= level:
+cdef int log(int level, action, obj, lineno) except -1:
+    if (<int> loglevel) >= level:
+        if reflog is None:
+            # can happen during finalisation
+            return 0
         reflog.append((lineno, action, id(obj)))
+    return 0
 
 LOG_NONE, LOG_ALL = range(2)
+cdef int _LOG_NONE = LOG_NONE
+cdef int _LOG_ALL = LOG_ALL
+
+cdef object NO_REFS = (0, None)
+
 
 @cython.final
 cdef class Context(object):
@@ -78,30 +84,35 @@ cdef class Context(object):
     def __dealloc__(self):
         __Pyx_refnanny_free_lock(self.lock)
 
-    cdef acquire_lock(self):
+    cdef void acquire_lock(self) noexcept:
         __Pyx_refnanny_lock_acquire(self.lock)
 
-    cdef release_lock(self):
+    cdef void release_lock(self) noexcept:
         __Pyx_refnanny_lock_release(self.lock)
 
-    cdef regref(self, obj, Py_ssize_t lineno, bint is_null):
-        log(LOG_ALL, u'regref', u"<NULL>" if is_null else obj, lineno)
+    cdef int regref(self, obj, Py_ssize_t lineno, bint is_null) except -1:
+        log(_LOG_ALL, u'regref', u"<NULL>" if is_null else obj, lineno)
         if is_null:
             self.errors.append(f"NULL argument on line {lineno}")
-            return
+            return 0
         id_ = id(obj)
-        count, linenumbers = self.refs.get(id_, (0, []))
+        count, linenumbers = self.refs.get(id_, NO_REFS)
+        if linenumbers is None:
+            linenumbers = []
         self.refs[id_] = (count + 1, linenumbers)
         linenumbers.append(lineno)
+        return 0
 
     cdef bint delref(self, obj, Py_ssize_t lineno, bint is_null) except -1:
         # returns whether it is ok to do the decref operation
-        log(LOG_ALL, u'delref', u"<NULL>" if is_null else obj, lineno)
+        log(_LOG_ALL, u'delref', u"<NULL>" if is_null else obj, lineno)
         if is_null:
             self.errors.append(f"NULL argument on line {lineno}")
             return False
         id_ = id(obj)
-        count, linenumbers = self.refs.get(id_, (0, []))
+        count, linenumbers = self.refs.get(id_, NO_REFS)
+        if linenumbers is None:
+            linenumbers = []
         if count == 0:
             self.errors.append(f"Too many decrefs on line {lineno}, reference acquired on lines {linenumbers!r}")
             return False
@@ -114,13 +125,13 @@ cdef class Context(object):
     cdef end(self):
         if self.refs:
             msg = u"References leaked:"
-            for count, linenos in self.refs.itervalues():
+            for count, linenos in self.refs.values():
                 msg += f"\n  ({count}) acquired on lines: {u', '.join([f'{x}' for x in linenos])}"
             self.errors.append(msg)
         return u"\n".join([f'REFNANNY: {error}' for error in self.errors]) if self.errors else None
 
 
-cdef void report_unraisable(filename, Py_ssize_t lineno, object e=None):
+cdef void report_unraisable(filename, Py_ssize_t lineno, object e=None) noexcept:
     try:
         if e is None:
             import sys
@@ -144,7 +155,7 @@ cdef PyObject* SetupContext(char* funcname, Py_ssize_t lineno, char* filename) e
     PyThreadState_Get()  # Check that we hold the GIL
     PyErr_Fetch(&type, &value, &tb)
     try:
-        ctx = Context(funcname, lineno, filename)
+        ctx = Context.__new__(Context, funcname, lineno, filename)
         Py_INCREF(ctx)
         result = <PyObject*>ctx
     except Exception, e:
@@ -152,41 +163,43 @@ cdef PyObject* SetupContext(char* funcname, Py_ssize_t lineno, char* filename) e
     PyErr_Restore(type, value, tb)
     return result
 
-cdef void GOTREF(PyObject* ctx, PyObject* p_obj, Py_ssize_t lineno):
-    if ctx == NULL: return
+cdef void GOTREF(PyObject* _ctx, PyObject* p_obj, Py_ssize_t lineno):
+    if _ctx == NULL: return
     cdef (PyObject*) type = NULL, value = NULL, tb = NULL
-    (<Context>ctx).acquire_lock()
+    cdef Context ctx = <Context> _ctx
+    ctx.acquire_lock()
     PyErr_Fetch(&type, &value, &tb)
     try:
-        (<Context>ctx).regref(
+        ctx.regref(
             <object>p_obj if p_obj is not NULL else None,
             lineno,
             is_null=p_obj is NULL,
         )
     except:
-        report_unraisable((<Context>ctx).filename, lineno=(<Context>ctx).start)
+        report_unraisable(ctx.filename, lineno=ctx.start)
     finally:
         PyErr_Restore(type, value, tb)
-        (<Context>ctx).release_lock()
+        ctx.release_lock()
         return  # swallow any exceptions
 
-cdef bint GIVEREF_and_report(PyObject* ctx, PyObject* p_obj, Py_ssize_t lineno):
-    if ctx == NULL: return 1
+cdef bint GIVEREF_and_report(PyObject* _ctx, PyObject* p_obj, Py_ssize_t lineno):
+    if _ctx == NULL: return 1
     cdef (PyObject*) type = NULL, value = NULL, tb = NULL
     cdef bint decref_ok = False
-    (<Context>ctx).acquire_lock()
+    cdef Context ctx = <Context> _ctx
+    ctx.acquire_lock()
     PyErr_Fetch(&type, &value, &tb)
     try:
-        decref_ok = (<Context>ctx).delref(
+        decref_ok = ctx.delref(
             <object>p_obj if p_obj is not NULL else None,
             lineno,
             is_null=p_obj is NULL,
         )
     except:
-        report_unraisable((<Context>ctx).filename, lineno=(<Context>ctx).start)
+        report_unraisable(ctx.filename, lineno=ctx.start)
     finally:
         PyErr_Restore(type, value, tb)
-        (<Context>ctx).release_lock()
+        ctx.release_lock()
         return decref_ok  # swallow any exceptions
 
 cdef void GIVEREF(PyObject* ctx, PyObject* p_obj, Py_ssize_t lineno):