diff --git a/rules-tests/CodingStyle/Rector/FuncCall/ConsistentPregDelimiterRector/Fixture/escape_content_delimiter_in_pattern.php.inc b/rules-tests/CodingStyle/Rector/FuncCall/ConsistentPregDelimiterRector/Fixture/escape_content_delimiter_in_pattern.php.inc
new file mode 100644
index 000000000000..856e1d249442
--- /dev/null
+++ b/rules-tests/CodingStyle/Rector/FuncCall/ConsistentPregDelimiterRector/Fixture/escape_content_delimiter_in_pattern.php.inc
@@ -0,0 +1,27 @@
+<?php
+
+namespace Rector\Tests\CodingStyle\Rector\FuncCall\ConsistentPregDelimiterRector\Fixture;
+
+class EscapeContentDelimiterInPattern
+{
+    public function run($value)
+    {
+        preg_match('/^#(([a-f0-9]{3}){1,2})$/i', '#ffffff');
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\CodingStyle\Rector\FuncCall\ConsistentPregDelimiterRector\Fixture;
+
+class EscapeContentDelimiterInPattern
+{
+    public function run($value)
+    {
+        preg_match('#^\#(([a-f0-9]{3}){1,2})$#i', '#ffffff');
+    }
+}
+
+?>
diff --git a/rules/CodingStyle/Rector/FuncCall/ConsistentPregDelimiterRector.php b/rules/CodingStyle/Rector/FuncCall/ConsistentPregDelimiterRector.php
index e037d2f8a086..0fb9acc68ffc 100644
--- a/rules/CodingStyle/Rector/FuncCall/ConsistentPregDelimiterRector.php
+++ b/rules/CodingStyle/Rector/FuncCall/ConsistentPregDelimiterRector.php
@@ -168,6 +168,8 @@ private function refactorArgument(Arg $arg): void
 
         $string->value = Strings::replace($value, self::INNER_REGEX, function (array $match): string {
             $innerPattern = $match['content'];
+            $innerPattern = str_replace($this->delimiter, '\\' . $this->delimiter, $innerPattern);
+
             // change delimiter
             if (strlen($innerPattern) > 2 && $innerPattern[0] === $innerPattern[strlen($innerPattern) - 1]) {
                 $innerPattern[0] = $this->delimiter;