diff --git a/src/Type/Regex/RegexExpressionHelper.php b/src/Type/Regex/RegexExpressionHelper.php
index 0334aead77..0df0dc011c 100644
--- a/src/Type/Regex/RegexExpressionHelper.php
+++ b/src/Type/Regex/RegexExpressionHelper.php
@@ -88,6 +88,8 @@ public function getPatternModifiers(string $pattern): ?string
 
 	public function removeDelimitersAndModifiers(string $pattern): string
 	{
+		$pattern = ltrim($pattern);
+
 		$endDelimiterPos = $this->getEndDelimiterPos($pattern);
 
 		if ($endDelimiterPos === false) {
diff --git a/tests/PHPStan/Analyser/nsrt/preg_match_shapes.php b/tests/PHPStan/Analyser/nsrt/preg_match_shapes.php
index 4b17f15ed4..f92af453fb 100644
--- a/tests/PHPStan/Analyser/nsrt/preg_match_shapes.php
+++ b/tests/PHPStan/Analyser/nsrt/preg_match_shapes.php
@@ -768,3 +768,13 @@ function bug11604b (string $string): void {
 		assertType("array{0: string, 1?: ''|'XX', 2?: ''|'YY', 3?: 'ZZ'}", $matches);
 	}
 }
+
+function testLtrimDelimiter (string $string): void {
+	if (preg_match(' /(x)/', $string, $matches)) {
+		assertType("array{string, 'x'}", $matches);
+	}
+
+	if (preg_match('  /(x)/', $string, $matches)) {
+		assertType("array{string, 'x'}", $matches);
+	}
+}
diff --git a/tests/PHPStan/Type/Regex/RegexExpressionHelperTest.php b/tests/PHPStan/Type/Regex/RegexExpressionHelperTest.php
new file mode 100644
index 0000000000..330594145f
--- /dev/null
+++ b/tests/PHPStan/Type/Regex/RegexExpressionHelperTest.php
@@ -0,0 +1,61 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Regex;
+
+use PHPStan\Testing\PHPStanTestCase;
+
+class RegexExpressionHelperTest extends PHPStanTestCase
+{
+
+	public function dataRemoveDelimitersAndModifiers(): array
+	{
+		return [
+			[
+				'/x/',
+				'x',
+			],
+			[
+				'~x~',
+				'x',
+			],
+			[
+				'~~',
+				'',
+			],
+			[
+				'~x~is',
+				'x',
+			],
+			[
+				' ~x~',
+				'x',
+			],
+			[
+				'  ~x~  ',
+				'x',
+			],
+			[
+				'[x]',
+				'x',
+			],
+			[
+				'{x}mx',
+				'x',
+			],
+		];
+	}
+
+	/**
+	 * @dataProvider dataRemoveDelimitersAndModifiers
+	 */
+	public function testRemoveDelimitersAndModifiers(string $inputPattern, string $expectedPatternWithoutDelimiter): void
+	{
+		$regexExpressionHelper = self::getContainer()->getByType(RegexExpressionHelper::class);
+
+		$this->assertSame(
+			$expectedPatternWithoutDelimiter,
+			$regexExpressionHelper->removeDelimitersAndModifiers($inputPattern),
+		);
+	}
+
+}