diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 81774dc..23d7aa4 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -29,6 +29,9 @@
 int Py_HasFileSystemDefaultEncoding = 0;
 #endif
 const char *Py_FileSystemDefaultEncodeErrors = "surrogateescape";
+/* UTF-8 mode (PEP 540): if non-zero, use the UTF-8 encoding, and change stdin
+   and stdout error handler to "surrogateescape". */
+int Py_UTF8Mode = 0;
 
 _Py_IDENTIFIER(__builtins__);
 _Py_IDENTIFIER(__dict__);