diff --git a/conf/config.neon b/conf/config.neon
index 5ad99397a9..7c88f87a31 100644
--- a/conf/config.neon
+++ b/conf/config.neon
@@ -733,6 +733,11 @@ services:
 		tags:
 			- phpstan.parser.richParserNodeVisitor
 
+	-
+		class: PHPStan\Parser\ImmediatelyInvokedClosureVisitor
+		tags:
+			- phpstan.parser.richParserNodeVisitor
+
 	-
 		class: PHPStan\Parallel\ParallelAnalyser
 		arguments:
diff --git a/src/Analyser/MutatingScope.php b/src/Analyser/MutatingScope.php
index 90b3fdd465..2724ba1fca 100644
--- a/src/Analyser/MutatingScope.php
+++ b/src/Analyser/MutatingScope.php
@@ -46,6 +46,7 @@
 use PHPStan\Node\Printer\ExprPrinter;
 use PHPStan\Node\PropertyAssignNode;
 use PHPStan\Parser\ArrayMapArgVisitor;
+use PHPStan\Parser\ImmediatelyInvokedClosureVisitor;
 use PHPStan\Parser\NewAssignedToPropertyVisitor;
 use PHPStan\Parser\Parser;
 use PHPStan\Php\PhpVersion;
@@ -4794,6 +4795,7 @@ private function processFinallyScopeVariableTypeHolders(
 	 * @param Expr\ClosureUse[] $byRefUses
 	 */
 	public function processClosureScope(
+		Expr\Closure $expr,
 		self $closureScope,
 		?self $prevScope,
 		array $byRefUses,
@@ -4826,7 +4828,9 @@ public function processClosureScope(
 				$prevVariableType = $prevScope->getVariableType($variableName);
 				if (!$variableType->equals($prevVariableType)) {
 					$variableType = TypeCombinator::union($variableType, $prevVariableType);
-					$variableType = self::generalizeType($variableType, $prevVariableType, 0);
+					if ($expr->getAttribute(ImmediatelyInvokedClosureVisitor::ATTRIBUTE_NAME) !== true) {
+						$variableType = self::generalizeType($variableType, $prevVariableType, 0);
+					}
 				}
 			}
 
diff --git a/src/Analyser/NodeScopeResolver.php b/src/Analyser/NodeScopeResolver.php
index 5831cdaaaf..fd6ac13fc3 100644
--- a/src/Analyser/NodeScopeResolver.php
+++ b/src/Analyser/NodeScopeResolver.php
@@ -4232,7 +4232,7 @@ private function processClosureNode(
 		}
 
 		$closureScope = $scope->enterAnonymousFunction($expr, $callableParameters);
-		$closureScope = $closureScope->processClosureScope($scope, null, $byRefUses);
+		$closureScope = $closureScope->processClosureScope($expr, $scope, null, $byRefUses);
 		$closureType = $closureScope->getAnonymousFunctionReflection();
 		if (!$closureType instanceof ClosureType) {
 			throw new ShouldNotHappenException();
@@ -4302,7 +4302,7 @@ private function processClosureNode(
 				$intermediaryClosureScope = $intermediaryClosureScope->mergeWith($exitPoint->getScope());
 			}
 			$closureScope = $scope->enterAnonymousFunction($expr, $callableParameters);
-			$closureScope = $closureScope->processClosureScope($intermediaryClosureScope, $prevScope, $byRefUses);
+			$closureScope = $closureScope->processClosureScope($expr, $intermediaryClosureScope, $prevScope, $byRefUses);
 			if ($closureScope->equals($prevScope)) {
 				break;
 			}
@@ -4322,7 +4322,7 @@ private function processClosureNode(
 			array_merge($statementResult->getImpurePoints(), $closureImpurePoints),
 		), $closureScope);
 
-		return new ProcessClosureResult($scope->processClosureScope($closureScope, null, $byRefUses), $statementResult->getThrowPoints(), $statementResult->getImpurePoints(), $invalidateExpressions);
+		return new ProcessClosureResult($scope->processClosureScope($expr, $closureScope, null, $byRefUses), $statementResult->getThrowPoints(), $statementResult->getImpurePoints(), $invalidateExpressions);
 	}
 
 	/**
diff --git a/src/Parser/ImmediatelyInvokedClosureVisitor.php b/src/Parser/ImmediatelyInvokedClosureVisitor.php
new file mode 100644
index 0000000000..c77059e214
--- /dev/null
+++ b/src/Parser/ImmediatelyInvokedClosureVisitor.php
@@ -0,0 +1,22 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Parser;
+
+use PhpParser\Node;
+use PhpParser\NodeVisitorAbstract;
+
+final class ImmediatelyInvokedClosureVisitor extends NodeVisitorAbstract
+{
+
+	public const ATTRIBUTE_NAME = 'isImmediatelyInvokedClosure';
+
+	public function enterNode(Node $node): ?Node
+	{
+		if ($node instanceof Node\Expr\FuncCall && $node->name instanceof Node\Expr\Closure) {
+			$node->name->setAttribute(self::ATTRIBUTE_NAME, true);
+		}
+
+		return null;
+	}
+
+}
diff --git a/tests/PHPStan/Analyser/nsrt/bug-11561.php b/tests/PHPStan/Analyser/nsrt/bug-11561.php
new file mode 100644
index 0000000000..1a01e5f97a
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-11561.php
@@ -0,0 +1,40 @@
+<?php // lint >= 8.0
+
+namespace Bug11561;
+
+use function PHPStan\Testing\assertType;
+use DateTime;
+
+/** @param array{date: DateTime} $c */
+function main(mixed $c): void{
+	assertType('array{date: DateTime}', $c);
+	$c['id']=1;
+	assertType('array{date: DateTime, id: 1}', $c);
+
+	$x = (function() use (&$c) {
+		assertType("array{date: DateTime, id: 1, name?: 'ruud'}", $c);
+		$c['name'] = 'ruud';
+		assertType("array{date: DateTime, id: 1, name: 'ruud'}", $c);
+		return 'x';
+	})();
+
+	assertType("array{date: DateTime, id: 1, name?: 'ruud'}", $c);
+}
+
+
+/** @param array{date: DateTime} $c */
+function main2(mixed $c): void{
+	assertType('array{date: DateTime}', $c);
+	$c['id']=1;
+	$c['name'] = 'staabm';
+	assertType("array{date: DateTime, id: 1, name: 'staabm'}", $c);
+
+	$x = (function() use (&$c) {
+		assertType("array{date: DateTime, id: 1, name: 'ruud'|'staabm'}", $c);
+		$c['name'] = 'ruud';
+		assertType("array{date: DateTime, id: 1, name: 'ruud'}", $c);
+		return 'x';
+	})();
+
+	assertType("array{date: DateTime, id: 1, name: 'ruud'|'staabm'}", $c);
+}