diff --git a/Lib/plistlib.py b/Lib/plistlib.py
index 21ebec3f004590..33b79a133b0a84 100644
--- a/Lib/plistlib.py
+++ b/Lib/plistlib.py
@@ -929,7 +929,7 @@ def _is_fmt_binary(header):
 
 
 def load(fp, *, fmt=None, use_builtin_types=True, dict_type=dict):
-    """Read a .plist file. 'fp' should be (readable) file object.
+    """Read a .plist file. 'fp' should be a readable and binary file object.
     Return the unpacked root object (which usually is a dictionary).
     """
     if fmt is None:
@@ -960,8 +960,8 @@ def loads(value, *, fmt=None, use_builtin_types=True, dict_type=dict):
 
 
 def dump(value, fp, *, fmt=FMT_XML, sort_keys=True, skipkeys=False):
-    """Write 'value' to a .plist file. 'fp' should be a (writable)
-    file object.
+    """Write 'value' to a .plist file. 'fp' should be a writable,
+    binary file object.
     """
     if fmt not in _FORMATS:
         raise ValueError("Unsupported format: %r"%(fmt,))