Implemented PEP 405 (Python virtual environments).
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index c434b5a..57f880e 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1528,6 +1528,10 @@
                         PyUnicode_FromWideChar(Py_GetPrefix(), -1));
     SET_SYS_FROM_STRING("exec_prefix",
                         PyUnicode_FromWideChar(Py_GetExecPrefix(), -1));
+    SET_SYS_FROM_STRING("base_prefix",
+                        PyUnicode_FromWideChar(Py_GetPrefix(), -1));
+    SET_SYS_FROM_STRING("base_exec_prefix",
+                        PyUnicode_FromWideChar(Py_GetExecPrefix(), -1));
     SET_SYS_FROM_STRING("maxsize",
                         PyLong_FromSsize_t(PY_SSIZE_T_MAX));
     SET_SYS_FROM_STRING("float_info",