diff --git a/Python/import.c b/Python/import.c
index e191bd5..8094f7d 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -950,8 +950,11 @@
 		if (Py_VerboseFlag)
 			PySys_WriteStderr("import %s # from %s\n",
 				name, pathname);
-		if (cpathname)
-			write_compiled_module(co, cpathname, mtime);
+		if (cpathname) {
+			PyObject *ro = PySys_GetObject("dont_write_bytecode");
+			if (ro == NULL || !PyObject_IsTrue(ro))
+				write_compiled_module(co, cpathname, mtime);
+		}
 	}
 	m = PyImport_ExecCodeModuleEx(name, (PyObject *)co, pathname);
 	Py_DECREF(co);
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index adae679..4939f54 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -72,6 +72,7 @@
 int Py_InteractiveFlag; /* Needed by Py_FdIsInteractive() below */
 int Py_InspectFlag; /* Needed to determine whether to exit at SystemError */
 int Py_NoSiteFlag; /* Suppress 'import site' */
+int Py_DontWriteBytecodeFlag; /* Suppress writing bytecode files (*.py[co]) */
 int Py_UseClassExceptionsFlag = 1; /* Needed by bltinmodule.c: deprecated */
 int Py_FrozenFlag; /* Needed by getpath.c */
 int Py_UnicodeFlag = 0; /* Needed by compile.c */
@@ -172,6 +173,8 @@
 		Py_VerboseFlag = add_flag(Py_VerboseFlag, p);
 	if ((p = Py_GETENV("PYTHONOPTIMIZE")) && *p != '\0')
 		Py_OptimizeFlag = add_flag(Py_OptimizeFlag, p);
+	if ((p = Py_GETENV("PYTHONDONTWRITEBYTECODE")) && *p != '\0')
+		Py_DontWriteBytecodeFlag = add_flag(Py_DontWriteBytecodeFlag, p);
 
 	interp = PyInterpreterState_New();
 	if (interp == NULL)
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 2a6a8c3..bd551b5 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1128,6 +1128,9 @@
 	v = Py_BuildValue("(ssz)", "CPython", branch, svn_revision);
 	PyDict_SetItemString(sysdict, "subversion", v);
 	Py_XDECREF(v);
+        PyDict_SetItemString(sysdict, "dont_write_bytecode",
+                             v = PyBool_FromLong(Py_DontWriteBytecodeFlag));
+        Py_XDECREF(v);
 	/*
 	 * These release level checks are mutually exclusive and cover
 	 * the field, so don't get too fancy with the pre-processor!