diff --git a/README.rst b/README.rst
index 79380da0c..9d737f065 100644
--- a/README.rst
+++ b/README.rst
@@ -193,7 +193,7 @@ The `open` function also works as a context handler:
     The ``copy_arrays`` argument of `asdf.open()` and `AsdfFile` is deprecated,
     and will be removed in ASDF 4.0. It is replaced by ``memmap``, which
     is the opposite of ``copy_arrays`` (``memmap == not copy_arrays``).
-    In ASDF 4.0, ``memmap`` will default to ``False``, which means arrays 
+    In ASDF 4.0, ``memmap`` will default to ``False``, which means arrays
     will no longer be memory-mapped by default.
 
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