diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index e8f4fa2..e83c4cb 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -275,7 +275,8 @@
 		sys_isatty = PyObject_CallMethod(sys_stream, "isatty", "");
 		if (!sys_isatty)
 			PyErr_Clear();
-		if(sys_isatty && PyObject_IsTrue(sys_isatty)) {
+		if(sys_isatty && PyObject_IsTrue(sys_isatty) &&
+		   PyFile_Check(sys_stream)) {
 			if (!PyFile_SetEncoding(sys_stream, codeset))
 				Py_FatalError("Cannot set codeset of stdin");
 		}
@@ -285,7 +286,8 @@
 		sys_isatty = PyObject_CallMethod(sys_stream, "isatty", "");
 		if (!sys_isatty)
 			PyErr_Clear();
-		if(sys_isatty && PyObject_IsTrue(sys_isatty)) {
+		if(sys_isatty && PyObject_IsTrue(sys_isatty) &&
+		   PyFile_Check(sys_stream)) {
 			if (!PyFile_SetEncoding(sys_stream, codeset))
 				Py_FatalError("Cannot set codeset of stdout");
 		}
@@ -295,7 +297,8 @@
 		sys_isatty = PyObject_CallMethod(sys_stream, "isatty", "");
 		if (!sys_isatty)
 			PyErr_Clear();
-		if(sys_isatty && PyObject_IsTrue(sys_isatty)) {
+		if(sys_isatty && PyObject_IsTrue(sys_isatty) &&
+		   PyFile_Check(sys_stream)) {
 			if (!PyFile_SetEncoding(sys_stream, codeset))
 				Py_FatalError("Cannot set codeset of stderr");
 		}
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 4970adf..59f6cfc 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1087,17 +1087,17 @@
 	if (PyErr_Occurred())
 		return NULL;
 #ifdef MS_WINDOWS
-	if(isatty(_fileno(stdin))){
+	if(isatty(_fileno(stdin)) && PyFile_Check(sysin)) {
 		sprintf(buf, "cp%d", GetConsoleCP());
 		if (!PyFile_SetEncoding(sysin, buf))
 			return NULL;
 	}
-	if(isatty(_fileno(stdout))) {
+	if(isatty(_fileno(stdout)) && PyFile_Check(sysout)) {
 		sprintf(buf, "cp%d", GetConsoleOutputCP());
 		if (!PyFile_SetEncoding(sysout, buf))
 			return NULL;
 	}
-	if(isatty(_fileno(stderr))) {
+	if(isatty(_fileno(stderr)) && PyFile_Check(syserr)) {
 		sprintf(buf, "cp%d", GetConsoleOutputCP());
 		if (!PyFile_SetEncoding(syserr, buf))
 			return NULL;