diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2064f81f..506b6b1b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,8 @@ Please also have a look at our
 
 ### Changed
 
+- `DeclarationBlock` no longer extends `RuleSet` and instead has a `RuleSet` as
+  a property; use `getRuleSet()` to access it directly (#1194)
 - The default line (and column) number is now `null` (not zero) (#1288)
 - `setPosition()` (in `Rule` and other classes) now has fluent interface,
   returning itself (#1259)
diff --git a/README.md b/README.md
index 29253a34..b6008004 100644
--- a/README.md
+++ b/README.md
@@ -753,7 +753,11 @@ classDiagram
     CSSFunction <|-- Color: inheritance
     Positionable <|.. Comment: realization
     Renderable <|.. Comment: realization
-    RuleSet <|-- DeclarationBlock: inheritance
+    CSSElement <|.. DeclarationBlock: realization
+    CSSListItem <|.. DeclarationBlock: realization
+    Positionable <|.. DeclarationBlock: realization
+    RuleContainer <|.. DeclarationBlock: realization
+    DeclarationBlock ..> RuleSet : dependency
     DeclarationBlock ..> Selector: dependency
     CSSBlockList <|-- Document: inheritance
     AtRule <|.. Import: realization
diff --git a/src/CSSList/CSSBlockList.php b/src/CSSList/CSSBlockList.php
index 2dfd284f..122ac5d1 100644
--- a/src/CSSList/CSSBlockList.php
+++ b/src/CSSList/CSSBlockList.php
@@ -56,6 +56,8 @@ public function getAllRuleSets(): array
                 $result[] = $item;
             } elseif ($item instanceof CSSBlockList) {
                 $result = \array_merge($result, $item->getAllRuleSets());
+            } elseif ($item instanceof DeclarationBlock) {
+                $result[] = $item->getRuleSet();
             }
         }
 
diff --git a/src/RuleSet/DeclarationBlock.php b/src/RuleSet/DeclarationBlock.php
index 68926deb..4d077546 100644
--- a/src/RuleSet/DeclarationBlock.php
+++ b/src/RuleSet/DeclarationBlock.php
@@ -4,15 +4,21 @@
 
 namespace Sabberworm\CSS\RuleSet;
 
+use Sabberworm\CSS\Comment\CommentContainer;
+use Sabberworm\CSS\CSSElement;
 use Sabberworm\CSS\CSSList\CSSList;
+use Sabberworm\CSS\CSSList\CSSListItem;
 use Sabberworm\CSS\CSSList\KeyFrame;
 use Sabberworm\CSS\OutputFormat;
 use Sabberworm\CSS\Parsing\OutputException;
 use Sabberworm\CSS\Parsing\ParserState;
 use Sabberworm\CSS\Parsing\UnexpectedEOFException;
 use Sabberworm\CSS\Parsing\UnexpectedTokenException;
+use Sabberworm\CSS\Position\Position;
+use Sabberworm\CSS\Position\Positionable;
 use Sabberworm\CSS\Property\KeyframeSelector;
 use Sabberworm\CSS\Property\Selector;
+use Sabberworm\CSS\Rule\Rule;
 
 /**
  * This class represents a `RuleSet` constrained by a `Selector`.
@@ -21,14 +27,33 @@
  * matching elements.
  *
  * Declaration blocks usually appear directly inside a `Document` or another `CSSList` (mostly a `MediaQuery`).
+ *
+ * Note that `CSSListItem` extends both `Commentable` and `Renderable`, so those interfaces must also be implemented.
  */
-class DeclarationBlock extends RuleSet
+class DeclarationBlock implements CSSElement, CSSListItem, Positionable, RuleContainer
 {
+    use CommentContainer;
+    use Position;
+
     /**
      * @var array<Selector|string>
      */
     private $selectors = [];
 
+    /**
+     * @var RuleSet
+     */
+    private $ruleSet;
+
+    /**
+     * @param int<1, max>|null $lineNumber
+     */
+    public function __construct(?int $lineNumber = null)
+    {
+        $this->ruleSet = new RuleSet($lineNumber);
+        $this->setPosition($lineNumber);
+    }
+
     /**
      * @throws UnexpectedTokenException
      * @throws UnexpectedEOFException
@@ -107,7 +132,9 @@ public static function parse(ParserState $parserState, ?CSSList $list = null): ?
             }
         }
         $result->setComments($comments);
-        RuleSet::parseRuleSet($parserState, $result);
+
+        RuleSet::parseRuleSet($parserState, $result->getRuleSet());
+
         return $result;
     }
 
@@ -175,6 +202,73 @@ public function getSelectors(): array
         return $this->selectors;
     }
 
+    public function getRuleSet(): RuleSet
+    {
+        return $this->ruleSet;
+    }
+
+    /**
+     * @see RuleSet::addRule()
+     */
+    public function addRule(Rule $ruleToAdd, ?Rule $sibling = null): void
+    {
+        $this->ruleSet->addRule($ruleToAdd, $sibling);
+    }
+
+    /**
+     * @see RuleSet::getRules()
+     *
+     * @return array<int<0, max>, Rule>
+     */
+    public function getRules(?string $searchPattern = null): array
+    {
+        return $this->ruleSet->getRules($searchPattern);
+    }
+
+    /**
+     * @see RuleSet::setRules()
+     *
+     * @param array<Rule> $rules
+     */
+    public function setRules(array $rules): void
+    {
+        $this->ruleSet->setRules($rules);
+    }
+
+    /**
+     * @see RuleSet::getRulesAssoc()
+     *
+     * @return array<string, Rule>
+     */
+    public function getRulesAssoc(?string $searchPattern = null): array
+    {
+        return $this->ruleSet->getRulesAssoc($searchPattern);
+    }
+
+    /**
+     * @see RuleSet::removeRule()
+     */
+    public function removeRule(Rule $ruleToRemove): void
+    {
+        $this->ruleSet->removeRule($ruleToRemove);
+    }
+
+    /**
+     * @see RuleSet::removeMatchingRules()
+     */
+    public function removeMatchingRules(string $searchPattern): void
+    {
+        $this->ruleSet->removeMatchingRules($searchPattern);
+    }
+
+    /**
+     * @see RuleSet::removeAllRules()
+     */
+    public function removeAllRules(): void
+    {
+        $this->ruleSet->removeAllRules();
+    }
+
     /**
      * @return non-empty-string
      *
@@ -198,7 +292,7 @@ public function render(OutputFormat $outputFormat): string
         );
         $result .= $outputFormat->getContentAfterDeclarationBlockSelectors();
         $result .= $formatter->spaceBeforeOpeningBrace() . '{';
-        $result .= $this->renderRules($outputFormat);
+        $result .= $this->ruleSet->render($outputFormat);
         $result .= '}';
         $result .= $outputFormat->getContentAfterDeclarationBlock();
 
diff --git a/tests/ParserTest.php b/tests/ParserTest.php
index 15af0fd7..0217eba9 100644
--- a/tests/ParserTest.php
+++ b/tests/ParserTest.php
@@ -38,7 +38,7 @@ final class ParserTest extends TestCase
     /**
      * @test
      */
-    public function parseForOneRuleSetReturnsDocumentWithOneRuleSet(): void
+    public function parseForOneDeclarationBlockReturnsDocumentWithOneDeclarationBlock(): void
     {
         $css = '.thing { left: 10px; }';
         $parser = new Parser($css);
@@ -49,7 +49,7 @@ public function parseForOneRuleSetReturnsDocumentWithOneRuleSet(): void
 
         $cssList = $document->getContents();
         self::assertCount(1, $cssList);
-        self::assertInstanceOf(RuleSet::class, $cssList[0]);
+        self::assertInstanceOf(DeclarationBlock::class, $cssList[0]);
     }
 
     /**
@@ -926,9 +926,9 @@ public function missingPropertyValueStrict(): void
     public function missingPropertyValueLenient(): void
     {
         $parsed = self::parsedStructureForFile('missing-property-value', Settings::create()->withLenientParsing(true));
-        $rulesets = $parsed->getAllRuleSets();
-        self::assertCount(1, $rulesets);
-        $block = $rulesets[0];
+        $declarationBlocks = $parsed->getAllDeclarationBlocks();
+        self::assertCount(1, $declarationBlocks);
+        $block = $declarationBlocks[0];
         self::assertInstanceOf(DeclarationBlock::class, $block);
         self::assertEquals([new Selector('div')], $block->getSelectors());
         $rules = $block->getRules();
@@ -1055,7 +1055,7 @@ public function commentExtracting(): void
         // $this->assertSame("* Number 5 *", $fooBarBlockComments[1]->getComment());
 
         // Declaration rules.
-        self::assertInstanceOf(RuleSet::class, $fooBarBlock);
+        self::assertInstanceOf(DeclarationBlock::class, $fooBarBlock);
         $fooBarRules = $fooBarBlock->getRules();
         $fooBarRule = $fooBarRules[0];
         $fooBarRuleComments = $fooBarRule->getComments();
@@ -1076,7 +1076,7 @@ public function commentExtracting(): void
         self::assertSame('* Number 10 *', $fooBarComments[0]->getComment());
 
         // Media -> declaration -> rule.
-        self::assertInstanceOf(RuleSet::class, $mediaRules[0]);
+        self::assertInstanceOf(DeclarationBlock::class, $mediaRules[0]);
         $fooBarRules = $mediaRules[0]->getRules();
         $fooBarChildComments = $fooBarRules[0]->getComments();
         self::assertCount(1, $fooBarChildComments);
@@ -1092,7 +1092,7 @@ public function flatCommentExtractingOneComment(): void
         $document = $parser->parse();
 
         $contents = $document->getContents();
-        self::assertInstanceOf(RuleSet::class, $contents[0]);
+        self::assertInstanceOf(DeclarationBlock::class, $contents[0]);
         $divRules = $contents[0]->getRules();
         $comments = $divRules[0]->getComments();
 
@@ -1109,7 +1109,7 @@ public function flatCommentExtractingTwoConjoinedCommentsForOneRule(): void
         $document = $parser->parse();
 
         $contents = $document->getContents();
-        self::assertInstanceOf(RuleSet::class, $contents[0]);
+        self::assertInstanceOf(DeclarationBlock::class, $contents[0]);
         $divRules = $contents[0]->getRules();
         $comments = $divRules[0]->getComments();
 
@@ -1127,7 +1127,7 @@ public function flatCommentExtractingTwoSpaceSeparatedCommentsForOneRule(): void
         $document = $parser->parse();
 
         $contents = $document->getContents();
-        self::assertInstanceOf(RuleSet::class, $contents[0]);
+        self::assertInstanceOf(DeclarationBlock::class, $contents[0]);
         $divRules = $contents[0]->getRules();
         $comments = $divRules[0]->getComments();
 
@@ -1145,7 +1145,7 @@ public function flatCommentExtractingCommentsForTwoRules(): void
         $document = $parser->parse();
 
         $contents = $document->getContents();
-        self::assertInstanceOf(RuleSet::class, $contents[0]);
+        self::assertInstanceOf(DeclarationBlock::class, $contents[0]);
         $divRules = $contents[0]->getRules();
         $rule1Comments = $divRules[0]->getComments();
         $rule2Comments = $divRules[1]->getComments();
diff --git a/tests/RuleSet/DeclarationBlockTest.php b/tests/RuleSet/DeclarationBlockTest.php
index 5aaf0662..63411a64 100644
--- a/tests/RuleSet/DeclarationBlockTest.php
+++ b/tests/RuleSet/DeclarationBlockTest.php
@@ -8,13 +8,12 @@
 use Sabberworm\CSS\OutputFormat;
 use Sabberworm\CSS\Parser;
 use Sabberworm\CSS\Rule\Rule;
-use Sabberworm\CSS\RuleSet\RuleSet;
+use Sabberworm\CSS\RuleSet\DeclarationBlock;
 use Sabberworm\CSS\Settings as ParserSettings;
 use Sabberworm\CSS\Value\Size;
 
 /**
  * @covers \Sabberworm\CSS\RuleSet\DeclarationBlock
- * @covers \Sabberworm\CSS\RuleSet\RuleSet
  */
 final class DeclarationBlockTest extends TestCase
 {
@@ -31,7 +30,7 @@ public function overrideRules(): void
         $contents = $document->getContents();
         $wrapper = $contents[0];
 
-        self::assertInstanceOf(RuleSet::class, $wrapper);
+        self::assertInstanceOf(DeclarationBlock::class, $wrapper);
         self::assertCount(2, $wrapper->getRules());
         $wrapper->setRules([$rule]);
 
@@ -52,7 +51,7 @@ public function ruleInsertion(): void
         $contents = $document->getContents();
         $wrapper = $contents[0];
 
-        self::assertInstanceOf(RuleSet::class, $wrapper);
+        self::assertInstanceOf(DeclarationBlock::class, $wrapper);
 
         $leftRules = $wrapper->getRules('left');
         self::assertCount(1, $leftRules);
diff --git a/tests/Unit/CSSList/CSSBlockListTest.php b/tests/Unit/CSSList/CSSBlockListTest.php
index 41f2b41f..ce7e5447 100644
--- a/tests/Unit/CSSList/CSSBlockListTest.php
+++ b/tests/Unit/CSSList/CSSBlockListTest.php
@@ -157,7 +157,7 @@ public function getAllRuleSetsWhenNoContentSetReturnsEmptyArray(): void
     /**
      * @test
      */
-    public function getAllRuleSetsReturnsOneDeclarationBlockDirectlySetAsContent(): void
+    public function getAllRuleSetsReturnsRuleSetFromOneDeclarationBlockDirectlySetAsContent(): void
     {
         $subject = new ConcreteCSSBlockList();
 
@@ -166,7 +166,7 @@ public function getAllRuleSetsReturnsOneDeclarationBlockDirectlySetAsContent():
 
         $result = $subject->getAllRuleSets();
 
-        self::assertSame([$declarationBlock], $result);
+        self::assertSame([$declarationBlock->getRuleSet()], $result);
     }
 
     /**
@@ -187,7 +187,7 @@ public function getAllRuleSetsReturnsOneAtRuleSetDirectlySetAsContent(): void
     /**
      * @test
      */
-    public function getAllRuleSetsReturnsMultipleDeclarationBlocksDirectlySetAsContents(): void
+    public function getAllRuleSetsReturnsRuleSetsFromMultipleDeclarationBlocksDirectlySetAsContents(): void
     {
         $subject = new ConcreteCSSBlockList();
 
@@ -197,7 +197,7 @@ public function getAllRuleSetsReturnsMultipleDeclarationBlocksDirectlySetAsConte
 
         $result = $subject->getAllRuleSets();
 
-        self::assertSame([$declarationBlock1, $declarationBlock2], $result);
+        self::assertSame([$declarationBlock1->getRuleSet(), $declarationBlock2->getRuleSet()], $result);
     }
 
     /**
@@ -219,7 +219,7 @@ public function getAllRuleSetsReturnsMultipleAtRuleSetsDirectlySetAsContents():
     /**
      * @test
      */
-    public function getAllRuleSetsReturnsDeclarationBlocksWithinAtRuleBlockList(): void
+    public function getAllRuleSetsReturnsRuleSetsFromDeclarationBlocksWithinAtRuleBlockList(): void
     {
         $subject = new ConcreteCSSBlockList();
 
@@ -230,7 +230,7 @@ public function getAllRuleSetsReturnsDeclarationBlocksWithinAtRuleBlockList(): v
 
         $result = $subject->getAllRuleSets();
 
-        self::assertSame([$declarationBlock], $result);
+        self::assertSame([$declarationBlock->getRuleSet()], $result);
     }
 
     /**
diff --git a/tests/Unit/RuleSet/DeclarationBlockTest.php b/tests/Unit/RuleSet/DeclarationBlockTest.php
index 3d85d98c..4b20e9fc 100644
--- a/tests/Unit/RuleSet/DeclarationBlockTest.php
+++ b/tests/Unit/RuleSet/DeclarationBlockTest.php
@@ -10,7 +10,9 @@
 use Sabberworm\CSS\Parsing\ParserState;
 use Sabberworm\CSS\Position\Positionable;
 use Sabberworm\CSS\Property\Selector;
+use Sabberworm\CSS\Rule\Rule;
 use Sabberworm\CSS\RuleSet\DeclarationBlock;
+use Sabberworm\CSS\RuleSet\RuleSet;
 use Sabberworm\CSS\Settings;
 use TRegx\PhpUnit\DataProviders\DataProvider;
 
@@ -19,6 +21,8 @@
  */
 final class DeclarationBlockTest extends TestCase
 {
+    use RuleContainerTest;
+
     /**
      * @var DeclarationBlock
      */
@@ -199,4 +203,79 @@ static function (Selector $selectorObject): string {
             $declarationBlock->getSelectors()
         );
     }
+
+    /**
+     * @test
+     */
+    public function getRuleSetOnVirginReturnsARuleSet(): void
+    {
+        $result = $this->subject->getRuleSet();
+
+        self::assertInstanceOf(RuleSet::class, $result);
+    }
+
+    /**
+     * @test
+     */
+    public function getRuleSetAfterRulesSetReturnsARuleSet(): void
+    {
+        $this->subject->setRules([new Rule('color')]);
+
+        $result = $this->subject->getRuleSet();
+
+        self::assertInstanceOf(RuleSet::class, $result);
+    }
+
+    /**
+     * @test
+     */
+    public function getRuleSetOnVirginReturnsObjectWithoutRules(): void
+    {
+        $result = $this->subject->getRuleSet();
+
+        self::assertSame([], $result->getRules());
+    }
+
+    /**
+     * @test
+     *
+     * @param list<string> $propertyNamesToSet
+     *
+     * @dataProvider providePropertyNames
+     */
+    public function getRuleSetReturnsObjectWithRulesSet(array $propertyNamesToSet): void
+    {
+        $rules = self::createRulesFromPropertyNames($propertyNamesToSet);
+        $this->subject->setRules($rules);
+
+        $result = $this->subject->getRuleSet();
+
+        self::assertSame($rules, $result->getRules());
+    }
+
+    /**
+     * @test
+     */
+    public function getRuleSetByDefaultReturnsObjectWithNullLineNumber(): void
+    {
+        $result = $this->subject->getRuleSet();
+
+        self::assertNull($result->getLineNumber());
+    }
+
+    /**
+     * @test
+     *
+     * @param int<1, max>|null $lineNumber
+     *
+     * @dataProvider provideLineNumber
+     */
+    public function getRuleSetReturnsObjectWithLineNumberPassedToConstructor(?int $lineNumber): void
+    {
+        $subject = new DeclarationBlock($lineNumber);
+
+        $result = $subject->getRuleSet();
+
+        self::assertSame($lineNumber, $result->getLineNumber());
+    }
 }