diff --git a/README.md b/README.md
index e5dd70db..adfa0c79 100644
--- a/README.md
+++ b/README.md
@@ -720,7 +720,6 @@ classDiagram
     class Comment {
     }
 
-    RuleSet <|-- DeclarationBlock: inheritance
     Renderable <|-- CSSListItem: inheritance
     Commentable <|-- CSSListItem: inheritance
     Positionable <|.. RuleSet: realization
@@ -752,6 +751,8 @@ classDiagram
     AtRule <|.. KeyFrame: realization
     CSSBlockList <|-- AtRuleBlockList: inheritance
     AtRule <|.. AtRuleBlockList: realization
+    Positionable <|.. DeclarationBlock: realization
+    CSSListItem <|.. DeclarationBlock: realization
     CSSFunction <|-- Color: inheritance
     PrimitiveValue <|-- URL: inheritance
     RuleValueList <|-- CalcRuleValueList: inheritance
@@ -781,6 +782,7 @@ classDiagram
     Charset --> "*" Comment : comments
     Charset --> "1" CSSString : charset
     DeclarationBlock --> "*" Selector : selectors
+    DeclarationBlock --> "*" RuleSet : ruleSet
     Import --> "*" Comment : comments
     OutputFormat --> "1" OutputFormat : nextLevelFormat
     OutputFormat --> "1" OutputFormatter : outputFormatter
diff --git a/config/phpstan-baseline.neon b/config/phpstan-baseline.neon
index 007667a5..716b897b 100644
--- a/config/phpstan-baseline.neon
+++ b/config/phpstan-baseline.neon
@@ -48,6 +48,12 @@ parameters:
 			count: 1
 			path: ../src/RuleSet/DeclarationBlock.php
 
+		-
+			message: '#^Parameters should have "Sabberworm\\CSS\\Rule\\Rule" types as the only types passed to this method$#'
+			identifier: typePerfect.narrowPublicClassMethodParamType
+			count: 1
+			path: ../src/RuleSet/DeclarationBlock.php
+
 		-
 			message: '#^Parameters should have "string" types as the only types passed to this method$#'
 			identifier: typePerfect.narrowPublicClassMethodParamType
@@ -55,15 +61,15 @@ parameters:
 			path: ../src/RuleSet/DeclarationBlock.php
 
 		-
-			message: '#^Only booleans are allowed in a negated boolean, string\|null given\.$#'
-			identifier: booleanNot.exprNotBoolean
+			message: '#^Parameters should have "string\|null" types as the only types passed to this method$#'
+			identifier: typePerfect.narrowPublicClassMethodParamType
 			count: 2
-			path: ../src/RuleSet/RuleSet.php
+			path: ../src/RuleSet/DeclarationBlock.php
 
 		-
-			message: '#^Parameters should have "string" types as the only types passed to this method$#'
-			identifier: typePerfect.narrowPublicClassMethodParamType
-			count: 1
+			message: '#^Only booleans are allowed in a negated boolean, string\|null given\.$#'
+			identifier: booleanNot.exprNotBoolean
+			count: 2
 			path: ../src/RuleSet/RuleSet.php
 
 		-
diff --git a/src/CSSList/CSSBlockList.php b/src/CSSList/CSSBlockList.php
index 40a6ff0a..0f48691e 100644
--- a/src/CSSList/CSSBlockList.php
+++ b/src/CSSList/CSSBlockList.php
@@ -68,6 +68,8 @@ public function getAllRuleSets(): array
                 $result[] = $item;
             } elseif ($item instanceof CSSBlockList) {
                 $result = \array_merge($result, $item->getAllRuleSets());
+            } elseif ($item instanceof DeclarationBlock) {
+                $result[] = $item->getRuleSet();
             }
         }
 
@@ -75,7 +77,7 @@ public function getAllRuleSets(): array
     }
 
     /**
-     * @param CSSList|Rule|RuleSet|Value $element
+     * @param CSSList|DeclarationBlock|Rule|RuleSet|Value $element
      * @param list<Value> $result
      */
     protected function allValues(
@@ -88,7 +90,7 @@ protected function allValues(
             foreach ($element->getContents() as $content) {
                 $this->allValues($content, $result, $searchString, $searchInFunctionArguments);
             }
-        } elseif ($element instanceof RuleSet) {
+        } elseif ($element instanceof RuleSet || $element instanceof DeclarationBlock) {
             foreach ($element->getRules($searchString) as $rule) {
                 $this->allValues($rule, $result, $searchString, $searchInFunctionArguments);
             }
diff --git a/src/RuleSet/DeclarationBlock.php b/src/RuleSet/DeclarationBlock.php
index e4125797..cf54e6a9 100644
--- a/src/RuleSet/DeclarationBlock.php
+++ b/src/RuleSet/DeclarationBlock.php
@@ -4,31 +4,55 @@
 
 namespace Sabberworm\CSS\RuleSet;
 
+use Sabberworm\CSS\Comment\CommentContainer;
 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`.
+ * This class includes a `RuleSet` constrained by a `Selector`.
  *
  * It contains an array of selector objects (comma-separated in the CSS) as well as the rules to be applied to the
  * 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 CSSListItem, Positionable
 {
+    use CommentContainer;
+    use Position;
+
     /**
      * @var array<Selector|string>
      */
     private $selectors = [];
 
+    /**
+     * @var RuleSet
+     */
+    private $ruleSet;
+
+    /**
+     * @param int<0, max> $lineNumber
+     */
+    public function __construct(int $lineNumber = 0)
+    {
+        $this->setPosition($lineNumber);
+        $this->ruleSet = new RuleSet($lineNumber);
+    }
+
     /**
      * @throws UnexpectedTokenException
      * @throws UnexpectedEOFException
@@ -67,7 +91,9 @@ public static function parse(ParserState $parserState, ?CSSList $list = null): ?
             }
         }
         $result->setComments($comments);
-        RuleSet::parseRuleSet($parserState, $result);
+
+        RuleSet::parseRuleSet($parserState, $result->ruleSet);
+
         return $result;
     }
 
@@ -135,6 +161,63 @@ 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()
+     *
+     * @param Rule|string|null $searchPattern
+     *
+     * @return array<int<0, max>, Rule>
+     */
+    public function getRules($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()
+     *
+     * @param Rule|string|null $searchPattern
+     *
+     * @return array<string, Rule>
+     */
+    public function getRulesAssoc($searchPattern = null): array
+    {
+        return $this->ruleSet->getRulesAssoc($searchPattern);
+    }
+
+    /**
+     * @see RuleSet::removeRule()
+     *
+     * @param Rule|string|null $searchPattern
+     */
+    public function removeRule($searchPattern): void
+    {
+        $this->ruleSet->removeRule($searchPattern);
+    }
+
     /**
      * @return non-empty-string
      *
@@ -158,7 +241,7 @@ 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/src/RuleSet/RuleSet.php b/src/RuleSet/RuleSet.php
index 1d5b2b4c..2489bee9 100644
--- a/src/RuleSet/RuleSet.php
+++ b/src/RuleSet/RuleSet.php
@@ -23,10 +23,9 @@
  * If you want to manipulate a `RuleSet`, use the methods `addRule(Rule $rule)`, `getRules()` and `removeRule($rule)`
  * (which accepts either a `Rule` or a rule name; optionally suffixed by a dash to remove all related rules).
  *
- * Note that `CSSListItem` extends both `Commentable` and `Renderable`,
- * so those interfaces must also be implemented by concrete subclasses.
+ * Note that `CSSListItem` extends both `Commentable` and `Renderable`, so those interfaces must also be implemented.
  */
-abstract class RuleSet implements CSSListItem, Positionable
+class RuleSet implements CSSListItem, Positionable
 {
     use CommentContainer;
     use Position;
@@ -250,6 +249,14 @@ public function removeRule($searchPattern): void
         }
     }
 
+    /**
+     * @internal
+     */
+    public function render(OutputFormat $outputFormat): string
+    {
+        return $this->renderRules($outputFormat);
+    }
+
     protected function renderRules(OutputFormat $outputFormat): string
     {
         $result = '';
diff --git a/tests/ParserTest.php b/tests/ParserTest.php
index f0fee35b..72601802 100644
--- a/tests/ParserTest.php
+++ b/tests/ParserTest.php
@@ -37,7 +37,7 @@ final class ParserTest extends TestCase
     /**
      * @test
      */
-    public function parseForOneRuleSetReturnsDocumentWithOneRuleSet(): void
+    public function parseForOneDeclarationBlockReturnsDocumentWithOneDeclarationBlock(): void
     {
         $css = '.thing { left: 10px; }';
         $parser = new Parser($css);
@@ -48,7 +48,7 @@ public function parseForOneRuleSetReturnsDocumentWithOneRuleSet(): void
 
         $cssList = $document->getContents();
         self::assertCount(1, $cssList);
-        self::assertInstanceOf(RuleSet::class, $cssList[0]);
+        self::assertInstanceOf(DeclarationBlock::class, $cssList[0]);
     }
 
     /**
@@ -928,9 +928,9 @@ 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 = $block->getRules();
@@ -985,6 +985,7 @@ public function lineNumbersParsing(): void
                 && !$contentItem instanceof CSSNamespace
                 && !$contentItem instanceof Import
                 && !$contentItem instanceof RuleSet
+                && !$contentItem instanceof DeclarationBlock
             ) {
                 self::fail('Content item is not of an expected type.  It\'s a `' . \get_class($contentItem) . '`.');
             }
@@ -994,6 +995,7 @@ public function lineNumbersParsing(): void
                     if (
                         !$block instanceof CSSList
                         && !$block instanceof RuleSet
+                        && !$block instanceof DeclarationBlock
                     ) {
                         self::fail(
                             'KeyFrame content item is not of an expected type.  It\'s a `' . \get_class($block) . '`.'
@@ -1076,7 +1078,7 @@ 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();
@@ -1097,7 +1099,7 @@ 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);
@@ -1113,7 +1115,7 @@ 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();
 
@@ -1130,7 +1132,7 @@ 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();
 
@@ -1148,7 +1150,7 @@ 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();
 
@@ -1166,7 +1168,7 @@ 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 0028288f..36b319fe 100644
--- a/tests/Unit/CSSList/CSSBlockListTest.php
+++ b/tests/Unit/CSSList/CSSBlockListTest.php
@@ -154,7 +154,7 @@ public function getAllRuleSetsWhenNoContentSetReturnsEmptyArray(): void
     /**
      * @test
      */
-    public function getAllRuleSetsReturnsOneDeclarationBlockDirectlySetAsContent(): void
+    public function getAllRuleSetsReturnsRuleSetFromOneDeclarationBlockDirectlySetAsContent(): void
     {
         $subject = new ConcreteCSSBlockList();
 
@@ -163,7 +163,7 @@ public function getAllRuleSetsReturnsOneDeclarationBlockDirectlySetAsContent():
 
         $result = $subject->getAllRuleSets();
 
-        self::assertSame([$declarationBlock], $result);
+        self::assertSame([$declarationBlock->getRuleSet()], $result);
     }
 
     /**
@@ -184,7 +184,7 @@ public function getAllRuleSetsReturnsOneAtRuleSetDirectlySetAsContent(): void
     /**
      * @test
      */
-    public function getAllRuleSetsReturnsMultipleDeclarationBlocksDirectlySetAsContents(): void
+    public function getAllRuleSetsReturnsRuleSetsFromMultipleDeclarationBlocksDirectlySetAsContents(): void
     {
         $subject = new ConcreteCSSBlockList();
 
@@ -194,7 +194,7 @@ public function getAllRuleSetsReturnsMultipleDeclarationBlocksDirectlySetAsConte
 
         $result = $subject->getAllRuleSets();
 
-        self::assertSame([$declarationBlock1, $declarationBlock2], $result);
+        self::assertSame([$declarationBlock1->getRuleSet(), $declarationBlock2->getRuleSet()], $result);
     }
 
     /**
@@ -216,7 +216,7 @@ public function getAllRuleSetsReturnsMultipleAtRuleSetsDirectlySetAsContents():
     /**
      * @test
      */
-    public function getAllRuleSetsReturnsDeclarationBlocksWithinAtRuleBlockList(): void
+    public function getAllRuleSetsReturnsRuleSetsFromDeclarationBlocksWithinAtRuleBlockList(): void
     {
         $subject = new ConcreteCSSBlockList();
 
@@ -227,7 +227,7 @@ public function getAllRuleSetsReturnsDeclarationBlocksWithinAtRuleBlockList(): v
 
         $result = $subject->getAllRuleSets();
 
-        self::assertSame([$declarationBlock], $result);
+        self::assertSame([$declarationBlock->getRuleSet()], $result);
     }
 
     /**