diff --git a/src/Type/Php/RegexArrayShapeMatcher.php b/src/Type/Php/RegexArrayShapeMatcher.php
index 63e44b3ea2..64bdf2d605 100644
--- a/src/Type/Php/RegexArrayShapeMatcher.php
+++ b/src/Type/Php/RegexArrayShapeMatcher.php
@@ -417,7 +417,20 @@ private function isGroupOptional(RegexCapturingGroup $captureGroup, TrinaryLogic
 	private function createGroupValueType(RegexCapturingGroup $captureGroup, TrinaryLogic $wasMatched, int $flags, bool $isTrailingOptional, bool $isLastGroup, bool $matchesAll): Type
 	{
 		if ($matchesAll) {
-			if (!$this->containsSetOrder($flags) && !$this->containsUnmatchedAsNull($flags, $matchesAll) && $captureGroup->isOptional()) {
+			if (
+				(
+					!$this->containsSetOrder($flags)
+					&& !$this->containsUnmatchedAsNull($flags, $matchesAll)
+					&& $captureGroup->isOptional()
+				)
+				||
+				(
+					$this->containsSetOrder($flags)
+					&& !$this->containsUnmatchedAsNull($flags, $matchesAll)
+					&& $captureGroup->isOptional()
+					&& !$isTrailingOptional
+				)
+			) {
 				$groupValueType = $this->getValueType(
 					TypeCombinator::union($captureGroup->getType(), new ConstantStringType('')),
 					$flags,
diff --git a/tests/PHPStan/Analyser/nsrt/preg_match_all_shapes.php b/tests/PHPStan/Analyser/nsrt/preg_match_all_shapes.php
index c415fca42f..7ed783a8e9 100644
--- a/tests/PHPStan/Analyser/nsrt/preg_match_all_shapes.php
+++ b/tests/PHPStan/Analyser/nsrt/preg_match_all_shapes.php
@@ -175,3 +175,12 @@ function doFoobarNull(string $s): void {
 		}
 	}
 }
+
+function bug11661(): void {
+	preg_match_all('/(ERR)?(.+)/', 'abc', $results, PREG_SET_ORDER);
+	assertType("list<array{string, ''|'ERR', non-empty-string}>", $results);
+
+	preg_match_all('/(ERR)?.+/', 'abc', $results, PREG_SET_ORDER);
+	assertType("list<array{0: string, 1?: 'ERR'}>", $results);
+
+}