diff --git a/Include/pyerrors.h b/Include/pyerrors.h
index b55fb4e7452..fedf91333df 100644
--- a/Include/pyerrors.h
+++ b/Include/pyerrors.h
@@ -185,10 +185,11 @@ PyAPI_FUNC(PyObject *) PyErr_NoMemory(void);
 PyAPI_FUNC(PyObject *) PyErr_SetFromErrno(PyObject *);
 PyAPI_FUNC(PyObject *) PyErr_SetFromErrnoWithFilenameObject(
 	PyObject *, PyObject *);
-PyAPI_FUNC(PyObject *) PyErr_SetFromErrnoWithFilename(PyObject *, char *);
+PyAPI_FUNC(PyObject *) PyErr_SetFromErrnoWithFilename(
+	PyObject *, const char *);
 #ifdef MS_WINDOWS
 PyAPI_FUNC(PyObject *) PyErr_SetFromErrnoWithUnicodeFilename(
-	PyObject *, Py_UNICODE *);
+	PyObject *, const Py_UNICODE *);
 #endif /* MS_WINDOWS */
 
 PyAPI_FUNC(PyObject *) PyErr_Format(PyObject *, const char *, ...)
diff --git a/Python/errors.c b/Python/errors.c
index 24dafca921a..9f040ad523e 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -371,7 +371,7 @@ PyErr_SetFromErrnoWithFilenameObject(PyObject *exc, PyObject *filenameObject)
 
 
 PyObject *
-PyErr_SetFromErrnoWithFilename(PyObject *exc, char *filename)
+PyErr_SetFromErrnoWithFilename(PyObject *exc, const char *filename)
 {
 	PyObject *name = filename ? PyString_FromString(filename) : NULL;
 	PyObject *result = PyErr_SetFromErrnoWithFilenameObject(exc, name);
@@ -381,7 +381,7 @@ PyErr_SetFromErrnoWithFilename(PyObject *exc, char *filename)
 
 #ifdef MS_WINDOWS
 PyObject *
-PyErr_SetFromErrnoWithUnicodeFilename(PyObject *exc, Py_UNICODE *filename)
+PyErr_SetFromErrnoWithUnicodeFilename(PyObject *exc, const Py_UNICODE *filename)
 {
 	PyObject *name = filename ?
 	                 PyUnicode_FromUnicode(filename, wcslen(filename)) :