diff --git a/src/Analyser/ClassNode.php b/src/Analyser/ClassNode.php
index d81ea041..5513064a 100644
--- a/src/Analyser/ClassNode.php
+++ b/src/Analyser/ClassNode.php
@@ -135,20 +135,40 @@ public function dependsOnNamespace(string $namespace): bool
 
     public function implementsInterface(string $interface): bool
     {
-        return in_array($interface, $this->implements, true)
-            || in_array($interface, $this->parentInterfaces, true);
+        return $this->matchesAnyClassLike($interface, $this->implements)
+            || $this->matchesAnyClassLike($interface, $this->parentInterfaces);
     }
 
     public function extendsClass(string $class): bool
     {
-        return $this->extends === $class
-            || in_array($class, $this->parentClasses, true);
+        if ($this->extends !== null && strcasecmp($this->extends, $class) === 0) {
+            return true;
+        }
+
+        return $this->matchesAnyClassLike($class, $this->parentClasses);
     }
 
     public function extendsInterface(string $interface): bool
     {
-        return in_array($interface, $this->interfaceExtends, true)
-            || in_array($interface, $this->parentInterfaces, true);
+        return $this->matchesAnyClassLike($interface, $this->interfaceExtends)
+            || $this->matchesAnyClassLike($interface, $this->parentInterfaces);
+    }
+
+    /**
+     * Class-like names are case-insensitive in PHP, unlike function and
+     * constant dependencies, so matching must not be case-sensitive.
+     *
+     * @param string[] $classLikes
+     */
+    private function matchesAnyClassLike(string $needle, array $classLikes): bool
+    {
+        foreach ($classLikes as $classLike) {
+            if (strcasecmp($classLike, $needle) === 0) {
+                return true;
+            }
+        }
+
+        return false;
     }
 
     public function callsFunction(string $function): bool
diff --git a/tests/Analyser/ClassNodeTest.php b/tests/Analyser/ClassNodeTest.php
index c39b19fd..5a1bd6aa 100644
--- a/tests/Analyser/ClassNodeTest.php
+++ b/tests/Analyser/ClassNodeTest.php
@@ -161,6 +161,68 @@ className:          'App\\Domain\\DieService',
         $this->assertFalse($usesExit->usesLanguageConstruct('include'));
     }
 
+    public function testImplementsInterfaceIsCaseInsensitive(): void
+    {
+        $classNode = new ClassNode(
+            className:        Foo::class,
+            file:             '/foo.php',
+            line:             1,
+            layer:            'Domain',
+            extends:          null,
+            isAbstract:       false,
+            isFinal:          true,
+            isInterface:      false,
+            isReadonly:       false,
+            implements:       ['App\\Contracts\\foointerface'],
+            parentInterfaces: ['App\\Contracts\\rootinterface'],
+        );
+
+        $this->assertTrue($classNode->implementsInterface('App\\Contracts\\FooInterface'));
+        $this->assertTrue($classNode->implementsInterface('App\\Contracts\\RootInterface'));
+        $this->assertFalse($classNode->implementsInterface('App\\Contracts\\OtherInterface'));
+    }
+
+    public function testExtendsClassIsCaseInsensitive(): void
+    {
+        $classNode = new ClassNode(
+            className:     Foo::class,
+            file:          '/foo.php',
+            line:          1,
+            layer:         'Domain',
+            extends:       'App\\Support\\baseclass',
+            isAbstract:    false,
+            isFinal:       true,
+            isInterface:   false,
+            isReadonly:    false,
+            parentClasses: ['App\\Support\\rootclass'],
+        );
+
+        $this->assertTrue($classNode->extendsClass('App\\Support\\BaseClass'));
+        $this->assertTrue($classNode->extendsClass('App\\Support\\RootClass'));
+        $this->assertFalse($classNode->extendsClass('App\\Support\\OtherClass'));
+    }
+
+    public function testExtendsInterfaceIsCaseInsensitive(): void
+    {
+        $classNode = new ClassNode(
+            className:        'App\\Contracts\\FooInterface',
+            file:             '/FooInterface.php',
+            line:             1,
+            layer:            'Contracts',
+            extends:          null,
+            isAbstract:       false,
+            isFinal:          false,
+            isInterface:      true,
+            isReadonly:       false,
+            interfaceExtends: ['App\\Contracts\\baseinterface'],
+            parentInterfaces: ['App\\Contracts\\rootinterface'],
+        );
+
+        $this->assertTrue($classNode->extendsInterface('App\\Contracts\\BaseInterface'));
+        $this->assertTrue($classNode->extendsInterface('App\\Contracts\\RootInterface'));
+        $this->assertFalse($classNode->extendsInterface('App\\Contracts\\OtherInterface'));
+    }
+
     public function testSetRecursiveParents(): void
     {
         $classNode = new ClassNode(