diff -r 618ea5612e83 Doc/c-api/sys.rst
--- a/Doc/c-api/sys.rst	Tue Nov 27 23:06:19 2012 +0200
+++ b/Doc/c-api/sys.rst	Wed Nov 28 17:10:34 2012 +1100
@@ -32,6 +32,15 @@
    own code.
 
 
+.. c:function:: int PyOS_PutEnv(const char *string)
+
+   Python's own version of :c:func:`putenv` to overcome the limitation that
+   an embedded interpreter can't have it's environment variables set
+   by the application embedding it when Python is loaded as a dynamic library.
+   *string* is the environment variable to set, taking the form ``NAME=VALUE``.
+   Returns ``0`` on success, ``-1`` on error.
+
+
 .. c:function:: PyOS_sighandler_t PyOS_getsig(int i)
 
    Return the current signal handler for signal *i*.  This is a thin wrapper around
diff -r 618ea5612e83 Include/pythonrun.h
--- a/Include/pythonrun.h	Tue Nov 27 23:06:19 2012 +0200
+++ b/Include/pythonrun.h	Wed Nov 28 17:10:34 2012 +1100
@@ -227,6 +227,8 @@
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(char *) PyOS_Readline(FILE *, FILE *, char *);
 #endif
+PyAPI_FUNC(int) PyOS_PutEnv(char *);
+
 PyAPI_DATA(int) (*PyOS_InputHook)(void);
 PyAPI_DATA(char) *(*PyOS_ReadlineFunctionPointer)(FILE *, FILE *, char *);
 #ifndef Py_LIMITED_API
diff -r 618ea5612e83 Python/pythonrun.c
--- a/Python/pythonrun.c	Tue Nov 27 23:06:19 2012 +0200
+++ b/Python/pythonrun.c	Wed Nov 28 17:10:34 2012 +1100
@@ -2607,6 +2607,19 @@
 #endif
 }
 
+/*
+ * Use our own setenv() because embedded applications may need to set
+ * the environment. (see issue #16129).
+ */
+int PyOS_PutEnv(char *string)
+{
+#ifdef MS_WINDOWS
+    return _putenv(string);
+#else
+    return putenv(string);
+#endif
+}
+
 /* Deprecated C API functions still provided for binary compatiblity */
 
 #undef PyParser_SimpleParseFile