diff --git a/src/Analyser/TypeSpecifier.php b/src/Analyser/TypeSpecifier.php
index 276d219dce..9af30f6191 100644
--- a/src/Analyser/TypeSpecifier.php
+++ b/src/Analyser/TypeSpecifier.php
@@ -575,10 +575,26 @@ public function specifyTypesInCondition(
 			if (!$scope instanceof MutatingScope) {
 				throw new ShouldNotHappenException();
 			}
+
 			$leftTypes = $this->specifyTypesInCondition($scope, $expr->left, $context, $rootExpr);
 			$rightScope = $scope->filterByTruthyValue($expr->left);
 			$rightTypes = $this->specifyTypesInCondition($rightScope, $expr->right, $context, $rootExpr);
-			$types = $context->true() ? $leftTypes->unionWith($rightTypes) : $leftTypes->normalize($scope)->intersectWith($rightTypes->normalize($rightScope));
+
+			if ($context->falsey()) {
+				$leftIsAlwaysTrue = $scope->getType($expr->left)->isTrue()->yes();
+				$rightIsAlwaysTrue = $scope->getType($expr->right)->isTrue()->yes();
+
+				if ($leftIsAlwaysTrue && !$rightIsAlwaysTrue) {
+					return $context->true() ? $rightTypes : $rightTypes->normalize($rightScope);
+				}
+				if ($rightIsAlwaysTrue && !$leftIsAlwaysTrue) {
+					return $context->true() ? $leftTypes : $leftTypes->normalize($scope);
+				}
+			}
+
+			$types = $context->true()
+				? $leftTypes->unionWith($rightTypes)
+				: $leftTypes->normalize($scope)->intersectWith($rightTypes->normalize($rightScope));
 			if ($context->false()) {
 				return new SpecifiedTypes(
 					$types->getSureTypes(),
@@ -599,10 +615,26 @@ public function specifyTypesInCondition(
 			if (!$scope instanceof MutatingScope) {
 				throw new ShouldNotHappenException();
 			}
+
 			$leftTypes = $this->specifyTypesInCondition($scope, $expr->left, $context, $rootExpr);
 			$rightScope = $scope->filterByFalseyValue($expr->left);
 			$rightTypes = $this->specifyTypesInCondition($rightScope, $expr->right, $context, $rootExpr);
-			$types = $context->true() ? $leftTypes->normalize($scope)->intersectWith($rightTypes->normalize($rightScope)) : $leftTypes->unionWith($rightTypes);
+
+			if ($context->truthy()) {
+				$leftIsAlwaysFalse = $scope->getType($expr->left)->isFalse()->yes();
+				$rightIsAlwaysFalse = $scope->getType($expr->right)->isFalse()->yes();
+
+				if ($leftIsAlwaysFalse && !$rightIsAlwaysFalse) {
+					return $context->true() ? $rightTypes->normalize($rightScope) : $rightTypes;
+				}
+				if ($rightIsAlwaysFalse && !$leftIsAlwaysFalse) {
+					return $context->true() ? $leftTypes->normalize($scope) : $leftTypes;
+				}
+			}
+
+			$types = $context->true()
+				? $leftTypes->normalize($scope)->intersectWith($rightTypes->normalize($rightScope))
+				: $leftTypes->unionWith($rightTypes);
 			if ($context->true()) {
 				return new SpecifiedTypes(
 					$types->getSureTypes(),
diff --git a/tests/PHPStan/Analyser/TypeSpecifierTest.php b/tests/PHPStan/Analyser/TypeSpecifierTest.php
index c2b21e92c4..492bc16ef7 100644
--- a/tests/PHPStan/Analyser/TypeSpecifierTest.php
+++ b/tests/PHPStan/Analyser/TypeSpecifierTest.php
@@ -70,7 +70,9 @@ protected function setUp(): void
 		$this->scope = $this->scope->assignVariable('barOrFalse', new UnionType([new ObjectType('Bar'), new ConstantBooleanType(false)]), new UnionType([new ObjectType('Bar'), new ConstantBooleanType(false)]));
 		$this->scope = $this->scope->assignVariable('stringOrFalse', new UnionType([new StringType(), new ConstantBooleanType(false)]), new UnionType([new StringType(), new ConstantBooleanType(false)]));
 		$this->scope = $this->scope->assignVariable('array', new ArrayType(new MixedType(), new MixedType()), new ArrayType(new MixedType(), new MixedType()));
+		$this->scope = $this->scope->assignVariable('arrayOrNull', new UnionType([new ArrayType(new MixedType(), new MixedType()), new NullType()]), new UnionType([new ArrayType(new MixedType(), new MixedType()), new NullType()]));
 		$this->scope = $this->scope->assignVariable('foo', new MixedType(), new MixedType());
+		$this->scope = $this->scope->assignVariable('mixed', new MixedType(), new MixedType());
 		$this->scope = $this->scope->assignVariable('classString', new ClassStringType(), new ClassStringType());
 		$this->scope = $this->scope->assignVariable('genericClassString', new GenericClassStringType(new ObjectType('Bar')), new GenericClassStringType(new ObjectType('Bar')));
 		$this->scope = $this->scope->assignVariable('object', new ObjectWithoutClassType(), new ObjectWithoutClassType());
@@ -349,9 +351,17 @@ public function dataCondition(): iterable
 					$this->createFunctionCall('is_int', 'foo'),
 					$this->createFunctionCall('is_string', 'bar'),
 				),
-				[],
+				['$foo' => 'int'],
 				['$foo' => '~int', '$bar' => '~string'],
 			],
+			[
+				new Expr\BinaryOp\BooleanOr(
+					$this->createFunctionCall('is_int', 'foo'),
+					$this->createFunctionCall('is_string', 'mixed'),
+				),
+				[],
+				['$foo' => '~int', '$mixed' => '~string'],
+			],
 			[
 				new Expr\BinaryOp\BooleanAnd(
 					new Expr\BinaryOp\BooleanOr(
@@ -648,19 +658,37 @@ public function dataCondition(): iterable
 			[
 				new Expr\Empty_(new Variable('array')),
 				[
-					'$array' => 'array{}|null',
+					'$array' => 'array{}',
 				],
 				[
 					'$array' => '~0|0.0|\'\'|\'0\'|array{}|false|null',
 				],
 			],
+			[
+				new Expr\Empty_(new Variable('arrayOrNull')),
+				[
+					'$arrayOrNull' => 'array{}|null',
+				],
+				[
+					'$arrayOrNull' => '~0|0.0|\'\'|\'0\'|array{}|false|null',
+				],
+			],
 			[
 				new BooleanNot(new Expr\Empty_(new Variable('array'))),
 				[
 					'$array' => '~0|0.0|\'\'|\'0\'|array{}|false|null',
 				],
 				[
-					'$array' => 'array{}|null',
+					'$array' => 'array{}',
+				],
+			],
+			[
+				new BooleanNot(new Expr\Empty_(new Variable('arrayOrNull'))),
+				[
+					'$arrayOrNull' => '~0|0.0|\'\'|\'0\'|array{}|false|null',
+				],
+				[
+					'$arrayOrNull' => 'array{}|null',
 				],
 			],
 			[
diff --git a/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php b/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php
index deacff9371..d4c70900b4 100644
--- a/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php
+++ b/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php
@@ -864,4 +864,10 @@ public function testBug10997(): void
 		]);
 	}
 
+	public function testBug11276(): void
+	{
+		$this->reportPossiblyNonexistentConstantArrayOffset = true;
+		$this->analyse([__DIR__ . '/data/bug-11276.php'], []);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Arrays/data/bug-11276.php b/tests/PHPStan/Rules/Arrays/data/bug-11276.php
new file mode 100644
index 0000000000..7594f72659
--- /dev/null
+++ b/tests/PHPStan/Rules/Arrays/data/bug-11276.php
@@ -0,0 +1,40 @@
+<?php declare(strict_types = 1);
+
+namespace Bug11276;
+
+class HelloWorld
+{
+	/**
+	 * @param array{from: string, to: string} $expected
+	 */
+	public function testLanguagesMatchingRegex(string $url, ?array $expected): void
+	{
+		preg_match('#\/(?<from>[a-z]{2})-(?<to>[a-z]{1}[a-z0-9]{1})\/#', $url, $matches);
+
+		foreach ($expected as $key => $value) {
+			if ($matches instanceof ArrayAccess || \array_key_exists($key, $matches)) {
+				$matches[$key];
+			}
+		}
+
+		foreach ($expected as $key => $value) {
+			if (\array_key_exists($key, $matches) || $matches instanceof ArrayAccess) {
+				$matches[$key];
+			}
+		}
+
+		foreach ($expected as $key => $value) {
+			if (!$matches instanceof ArrayAccess && !\array_key_exists($key, $matches)) {
+			} else {
+				$matches[$key];
+			}
+		}
+
+		foreach ($expected as $key => $value) {
+			if (!\array_key_exists($key, $matches) && !$matches instanceof ArrayAccess) {
+			} else {
+				$matches[$key];
+			}
+		}
+	}
+}