diff --git a/docs/users/changelog.md b/docs/users/changelog.md
index c1427df..1cf4408 100644
--- a/docs/users/changelog.md
+++ b/docs/users/changelog.md
@@ -3,6 +3,11 @@
 This log documents all Python API or CLI breaking backwards incompatible changes.
 Note that there is currently no guarantee for a stable Markdown formatting style across versions.
 
+## **unreleased**
+
+- Deprecated
+  - `mdformat.codepoints.ASCII_WHITESPACE`
+
 ## 0.7.19
 
 - Deprecated
diff --git a/src/mdformat/codepoints/__init__.py b/src/mdformat/codepoints/__init__.py
index 25cfe95..37929c1 100644
--- a/src/mdformat/codepoints/__init__.py
+++ b/src/mdformat/codepoints/__init__.py
@@ -5,8 +5,27 @@
     "ASCII_WHITESPACE",
 )
 
+import warnings
+
 from mdformat.codepoints._unicode_punctuation import UNICODE_PUNCTUATION
 from mdformat.codepoints._unicode_whitespace import UNICODE_WHITESPACE
 
 ASCII_CTRL = frozenset(chr(i) for i in range(32))
-ASCII_WHITESPACE = frozenset({chr(9), chr(10), chr(11), chr(12), chr(13), chr(32)})
+
+
+def __getattr__(name: str) -> frozenset[str]:
+    """Attribute getter fallback.
+
+    Used during the deprecation period of `ASCII_WHITESPACE`.
+    """
+    if name == "ASCII_WHITESPACE":
+        warnings.warn(
+            "ASCII_WHITESPACE is deprecated because CommonMark v0.30 no longer "
+            "defines ASCII whitespace.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return frozenset({chr(9), chr(10), chr(11), chr(12), chr(13), chr(32)})
+    raise AttributeError(
+        f"module {__name__!r} has no attribute {name!r}"
+    )  # pragma: no cover
diff --git a/src/mdformat/renderer/_util.py b/src/mdformat/renderer/_util.py
index c9313e9..45a17a4 100644
--- a/src/mdformat/renderer/_util.py
+++ b/src/mdformat/renderer/_util.py
@@ -65,9 +65,7 @@ def longest_consecutive_sequence(seq: str, char: str) -> int:
 
 def maybe_add_link_brackets(link: str) -> str:
     """Surround URI with brackets if required by spec."""
-    if not link or (
-        codepoints.ASCII_CTRL | codepoints.ASCII_WHITESPACE | {"(", ")"}
-    ).intersection(link):
+    if not link or (codepoints.ASCII_CTRL | {" ", "(", ")"}).intersection(link):
         return "<" + link + ">"
     return link
 
diff --git a/tests/test_api.py b/tests/test_api.py
index 20c8f80..ce90049 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -141,3 +141,8 @@ def test_mdrenderer_no_finalize(tmp_path):
     unfinalized = MDRenderer().render(tokens, {}, env, finalize=False)
     finalized = MDRenderer().render(tokens, {}, env)
     assert finalized == unfinalized + "\n\n[gl ref]: https://gitlab.com\n"
+
+
+def test_ascii_whitespace_deprecation():
+    with pytest.warns(DeprecationWarning):
+        mdformat.codepoints.ASCII_WHITESPACE