diff --git a/src/Runner/SniffRunner.php b/src/Runner/SniffRunner.php
index 4059d76..15e7e9a 100644
--- a/src/Runner/SniffRunner.php
+++ b/src/Runner/SniffRunner.php
@@ -62,7 +62,7 @@ public function run(ConfigData $config, ?array $overridePaths = null, ?array $di
 
             $changedLines = $diffLines !== null
                 ? $this->getChangedLinesForFile($file, $diffLines)
-                : [];
+                : null;
 
             $fileReport = $processor->processFile(
                 $file,
diff --git a/src/Runner/XmlFileProcessor.php b/src/Runner/XmlFileProcessor.php
index 549156e..39b9d05 100644
--- a/src/Runner/XmlFileProcessor.php
+++ b/src/Runner/XmlFileProcessor.php
@@ -30,8 +30,8 @@ public function __construct(
         $this->report = $report ?? new Report();
     }
 
-    /** @param list<int> $changedLines */
-    public function processFile(string $filePath, array $changedLines = [], string $reportPath = ''): FileReport
+    /** @param list<int>|null $changedLines */
+    public function processFile(string $filePath, ?array $changedLines = null, string $reportPath = ''): FileReport
     {
         $effectivePath = $reportPath !== '' ? $reportPath : $filePath;
         $fileReport = new FileReport($effectivePath);
@@ -51,23 +51,23 @@ public function processFile(string $filePath, array $changedLines = [], string $
         return $this->processContent($content, $effectivePath, $fileReport, $changedLines);
     }
 
-    /** @param list<int> $changedLines */
+    /** @param list<int>|null $changedLines */
     public function processString(
         string $xmlContent,
         string $pseudoPath = 'input.xml',
-        array $changedLines = [],
+        ?array $changedLines = null,
     ): FileReport {
         $fileReport = new FileReport($pseudoPath);
 
         return $this->processContent($xmlContent, $pseudoPath, $fileReport, $changedLines);
     }
 
-    /** @param list<int> $changedLines */
+    /** @param list<int>|null $changedLines */
     private function processContent(
         string $content,
         string $filePath,
         FileReport $fileReport,
-        array $changedLines = [],
+        ?array $changedLines = null,
     ): FileReport {
         $content = $this->preprocessor->process($content);
 
@@ -87,7 +87,7 @@ private function processContent(
             $this->report->addSniffTime($sniff->getCode(), microtime(true) - $start);
         }
 
-        if ($changedLines !== []) {
+        if ($changedLines !== null) {
             $violations = $this->filterRelevantViolations($violations, $document, $changedLines);
         }
 
diff --git a/tests/Unit/Runner/SniffRunnerTest.php b/tests/Unit/Runner/SniffRunnerTest.php
index 971803b..f6801a3 100644
--- a/tests/Unit/Runner/SniffRunnerTest.php
+++ b/tests/Unit/Runner/SniffRunnerTest.php
@@ -278,4 +278,41 @@ public function itScansAllFilesWhenNoDiffIsGiven(): void
 
         self::assertSame(2, $report->getFilesScanned());
     }
+
+    #[Test]
+    public function itReportsNoViolationsForFilesInDiffWithoutAddedLines(): void
+    {
+        $sniff = new class implements SniffInterface {
+            public function getCode(): string
+            {
+                return 'Test.ViolatingSniff';
+            }
+
+            public function process(\DOMDocument $document, string $content, string $filePath): array
+            {
+                return [
+                    new Violation(
+                        sniffCode: 'Test.ViolatingSniff',
+                        filePath: $filePath,
+                        line: 1,
+                        message: 'Test violation',
+                        severity: Severity::WARNING,
+                    ),
+                ];
+            }
+
+            public function setProperty(string $name, string $value): void
+            {
+            }
+        };
+
+        $config = $this->createConfig(sniffs: [new SniffEntry($sniff::class)]);
+        $runner = new SniffRunner();
+
+        $diffLines = ['sniff_runner/default/file_a.xml' => []];
+        $report = $runner->run($config, null, $diffLines);
+
+        self::assertSame(1, $report->getFilesScanned());
+        self::assertFalse($report->hasViolations());
+    }
 }
diff --git a/tests/Unit/Runner/XmlFileProcessorTest.php b/tests/Unit/Runner/XmlFileProcessorTest.php
index 7633e1a..6bd60b4 100644
--- a/tests/Unit/Runner/XmlFileProcessorTest.php
+++ b/tests/Unit/Runner/XmlFileProcessorTest.php
@@ -274,6 +274,24 @@ public function itKeepsInternalErrorsEvenWithDiffFiltering(): void
         self::assertSame('DocbookCS.Internal', $report->getViolations()[0]->sniffCode);
     }
 
+    #[Test]
+    public function itReportsNoViolationsInDiffModeWhenNoLinesWereAdded(): void
+    {
+        $sniff = $this->sniff([3, 5]);
+
+        $xml = $this->xml(
+            '<chapter>
+          <simpara>3</simpara>
+          <simpara>4</simpara>
+          <simpara>5</simpara>
+        </chapter>'
+        );
+
+        $report = $this->processor([$sniff])->processString($xml, 'f.xml', []);
+
+        self::assertSame(0, $report->getViolationCount());
+    }
+
     /** @param list<int> $lines */
     private function sniff(array $lines): SniffInterface
     {