diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 101a6e4..f17fd05 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1110,17 +1110,17 @@
 	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;