diff --git a/Lib/python/pyrun.swg b/Lib/python/pyrun.swg
index b2bcf50ed..b7822ac9b 100644
--- a/Lib/python/pyrun.swg
+++ b/Lib/python/pyrun.swg
@@ -1075,7 +1075,7 @@ SWIG_Python_ConvertFunctionPtr(PyObject *obj, void **ptr, swig_type_info *ty) {
     void *vptr = 0;
     
     /* here we get the method pointer for callbacks */
-    char *doc = (((PyCFunctionObject *)obj) -> m_ml -> ml_doc);
+    const char *doc = (((PyCFunctionObject *)obj) -> m_ml -> ml_doc);
     const char *desc = doc ? strstr(doc, "swig_ptr: ") : 0;
     if (desc) {
       desc = ty ? SWIG_UnpackVoidPtr(desc + 10, &vptr, ty->name) : 0;