diff --git a/parso/file_io.py b/parso/file_io.py
index dda48bb..b9a24f4 100644
--- a/parso/file_io.py
+++ b/parso/file_io.py
@@ -5,8 +5,11 @@ class FileIO:
     def __init__(self, path):
         self.path = path
 
-    def read(self):
-        with open(self.path) as f:
+    def read(self):  # Returns bytes/str
+        # We would like to read unicode here, but we cannot, because we are not
+        # sure if it is a valid unicode file. Therefore just read whatever is
+        # here.
+        with open(self.path, 'rb') as f:
             return f.read()
 
     def get_last_modified(self):
@@ -16,6 +19,9 @@ class FileIO:
         """
         return os.path.getmtime(self.path)
 
+    def __repr__(self):
+        return '%s(%s)' % (self.__class__.__name__, self.path)
+
 
 class KnownContentFileIO(FileIO):
     def __init__(self, path, content):
diff --git a/parso/grammar.py b/parso/grammar.py
index 938439d..68a944a 100644
--- a/parso/grammar.py
+++ b/parso/grammar.py
@@ -105,7 +105,8 @@ class Grammar(object):
             if module_node is not None:
                 return module_node
 
-        code = file_io.read()
+        if code is None:
+            code = file_io.read()
         code = python_bytes_to_unicode(code)
 
         lines = split_lines(code, keepends=True)