diff --git a/progress/helpers.py b/progress/helpers.py
index 9ed90b2..0cde44e 100644
--- a/progress/helpers.py
+++ b/progress/helpers.py
@@ -28,14 +28,14 @@ class WriteMixin(object):
         if message:
             self.message = message
 
-        if self.file.isatty():
+        if self.file and self.file.isatty():
             if self.hide_cursor:
                 print(HIDE_CURSOR, end='', file=self.file)
             print(self.message, end='', file=self.file)
             self.file.flush()
 
     def write(self, s):
-        if self.file.isatty():
+        if self.file and self.file.isatty():
             b = '\b' * self._width
             c = s.ljust(self._width)
             print(b + c, end='', file=self.file)
@@ -43,7 +43,7 @@ class WriteMixin(object):
             self.file.flush()
 
     def finish(self):
-        if self.file.isatty() and self.hide_cursor:
+        if self.file and self.file.isatty() and self.hide_cursor:
             print(SHOW_CURSOR, end='', file=self.file)
 
 
@@ -55,21 +55,21 @@ class WritelnMixin(object):
         if message:
             self.message = message
 
-        if self.file.isatty() and self.hide_cursor:
+        if self.file and self.file.isatty() and self.hide_cursor:
             print(HIDE_CURSOR, end='', file=self.file)
 
     def clearln(self):
-        if self.file.isatty():
+        if self.file and self.file.isatty():
             print('\r\x1b[K', end='', file=self.file)
 
     def writeln(self, line):
-        if self.file.isatty():
+        if self.file and self.file.isatty():
             self.clearln()
             print(line, end='', file=self.file)
             self.file.flush()
 
     def finish(self):
-        if self.file.isatty():
+        if self.file and self.file.isatty():
             print(file=self.file)
             if self.hide_cursor:
                 print(SHOW_CURSOR, end='', file=self.file)