diff --git a/src/Text/Pandoc/Writers/Docx/OpenXML.hs b/src/Text/Pandoc/Writers/Docx/OpenXML.hs
index 473f51e62..c3be160f0 100644
--- a/src/Text/Pandoc/Writers/Docx/OpenXML.hs
+++ b/src/Text/Pandoc/Writers/Docx/OpenXML.hs
@@ -25,7 +25,7 @@ import Control.Applicative ((<|>))
 import Control.Monad.Except (catchError)
 import Crypto.Hash (hashWith, SHA1(SHA1))
 import qualified Data.ByteString.Lazy as BL
-import Data.Char (isLetter, isSpace)
+import Data.Char (isLetter, isSpace, isAlphaNum)
 import Text.Pandoc.Char (isCJK)
 import Data.Ord (comparing)
 import Data.String (fromString)
@@ -1140,14 +1140,18 @@ wrapBookmark ident contents = do
   return $ Elem bookmarkStart : contents ++ [Elem bookmarkEnd]
 
 -- Word imposes a 40 character limit on bookmark names and requires
--- that they begin with a letter.  So we just use a hash of the
--- identifier when otherwise we'd have an illegal bookmark name.
+-- that they begin with a letter or @_@ and contain only letters,
+-- numbers or underscores. Bookmarks beginning with @_@ are
+-- hidden in the user interface (and in particular hidden from screen
+-- readers, which we want); these are to be used for cross-references.
+-- When the id is otherwise illegal we use a hash of the identifier.
 toBookmarkName :: Text -> Text
 toBookmarkName s
-  | Just (c, _) <- T.uncons s
-  , isLetter c
-  , T.length s <= 40 = s
-  | otherwise = T.pack $ 'X' : drop 1 (show (hashWith SHA1 (fromText s)))
+  | T.length s < 40
+  , T.all (\c -> isAlphaNum c || c == '_') s
+    = "_" <> s
+  | otherwise = "_" <> T.pack (drop 1 (show (hashWith SHA1 (fromText s))))
+  -- we drop 1 because a SHA1 is 40 characters and we need room for the `_`
 
 maxListLevel :: Int
 maxListLevel = 8
diff --git a/test/docx/golden/block_quotes.docx b/test/docx/golden/block_quotes.docx
index 00be50e4d..a56e2b6be 100644
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diff --git a/test/docx/golden/custom_style_preserve.docx b/test/docx/golden/custom_style_preserve.docx
index cd0b9b69a..66fa80775 100644
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diff --git a/test/docx/golden/headers.docx b/test/docx/golden/headers.docx
index 64a9d7a01..927319c56 100644
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diff --git a/test/docx/golden/image.docx b/test/docx/golden/image.docx
index cea29628a..6d406e047 100644
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diff --git a/test/docx/golden/links.docx b/test/docx/golden/links.docx
index e51a54f6f..e4771e734 100644
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diff --git a/test/docx/golden/lists.docx b/test/docx/golden/lists.docx
index fbea56b38..318f74abb 100644
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diff --git a/test/docx/golden/lists_div_bullets.docx b/test/docx/golden/lists_div_bullets.docx
index 07fbf73ba..d3733238b 100644
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diff --git a/test/docx/golden/nested_anchors_in_header.docx b/test/docx/golden/nested_anchors_in_header.docx
index 333eac410..8ef14a778 100644
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diff --git a/test/docx/golden/notes.docx b/test/docx/golden/notes.docx
index a8dd65878..5aef60373 100644
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diff --git a/test/docx/golden/tables-default-widths.docx b/test/docx/golden/tables-default-widths.docx
index e8e72c391..ac25a17cd 100644
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diff --git a/test/docx/golden/tables.docx b/test/docx/golden/tables.docx
index 63ccd94ee..0a3063bd7 100644
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