diff --git a/pep-3107.txt b/pep-3107.txt
index 0eefa0644..609f44c2c 100644
--- a/pep-3107.txt
+++ b/pep-3107.txt
@@ -161,8 +161,8 @@ Accessing Function Annotations
 
 Once compiled, a function's annotations are available via the
 function's ``func_annotations`` attribute.  This attribute is 
-a dictionary, mapping parameter names to an object representing 
-the evaluated annotation expression
+a mutable dictionary, mapping parameter names to an object
+representing the evaluated annotation expression
 
 There is a special key in the ``func_annotations`` mapping,
 ``"return"``.  This key is present only if an annotation was supplied
@@ -184,9 +184,9 @@ The ``return`` key was chosen because it cannot conflict with the name
 of a parameter; any attempt to use ``return`` as a parameter name
 would result in a ``SyntaxError``.
 
-``func_annotations`` is an empty dictionary if no there are no
-annotations on the function.  ``func_annotations`` is always an empty
-dictionary for functions created from ``lambda`` expressions.
+``func_annotations`` is an empty, mutable dictionary if there are no
+annotations on the function or if the functions was created from
+a ``lambda`` expression.
 
 Use Cases
 =========