diff --git a/CHANGELOG.md b/CHANGELOG.md
index f31a4a61..03ddaea4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,8 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 ### Deprecated
 
+- Deprecate `DeclarationBlock::expandShorthands()` (#558)
+
 ### Removed
 
 - Drop support for PHP < 7.2 (#420)
diff --git a/src/RuleSet/DeclarationBlock.php b/src/RuleSet/DeclarationBlock.php
index 23716724..85ca5144 100644
--- a/src/RuleSet/DeclarationBlock.php
+++ b/src/RuleSet/DeclarationBlock.php
@@ -181,6 +181,8 @@ public function getSelectors()
      * Splits shorthand declarations (e.g. `margin` or `font`) into their constituent parts.
      *
      * @return void
+     *
+     * @deprecated This will be removed without substitution in version 10.0.
      */
     public function expandShorthands()
     {