diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index 1a8c59bc0..ef32f08c1 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -2690,7 +2690,7 @@ def open(fp, mode="r"):
     :exception FileNotFoundError: If the file cannot be found.
     :exception PIL.UnidentifiedImageError: If the image cannot be opened and
        identified.
-    :exception ValueError: If the ``mode`` is not "r", or if a StringIO
+    :exception ValueError: If the ``mode`` is not "r", or if a ``StringIO``
        instance is used for ``fp``.
     """