diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 3b45e07613..37501d1395 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -1549,7 +1549,7 @@ parameters:
 
 		-
 			message: "#^Doing instanceof PHPStan\\\\Type\\\\Constant\\\\ConstantArrayType is error\\-prone and deprecated\\. Use Type\\:\\:getConstantArrays\\(\\) instead\\.$#"
-			count: 12
+			count: 10
 			path: src/Type/TypeCombinator.php
 
 		-
diff --git a/src/Type/TypeCombinator.php b/src/Type/TypeCombinator.php
index 8d641cbfe5..491b9eb302 100644
--- a/src/Type/TypeCombinator.php
+++ b/src/Type/TypeCombinator.php
@@ -354,7 +354,7 @@ private static function compareTypesInUnion(Type $a, Type $b): ?array
 				return [new HasOffsetValueType($a->getOffsetType(), self::union($a->getValueType(), $b->getValueType())), null];
 			}
 		}
-		if ($a instanceof ConstantArrayType && $b instanceof ConstantArrayType) {
+		if ($a->isConstantArray()->yes() && $b->isConstantArray()->yes()) {
 			return null;
 		}
 
diff --git a/tests/PHPStan/Analyser/NodeScopeResolverTest.php b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
index 9435bbeaa8..054f64348b 100644
--- a/tests/PHPStan/Analyser/NodeScopeResolverTest.php
+++ b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
@@ -226,6 +226,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-3915.php');
 
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-2378.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-9985.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6294.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-2580.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-9753.php');
diff --git a/tests/PHPStan/Analyser/data/bug-9985.php b/tests/PHPStan/Analyser/data/bug-9985.php
new file mode 100644
index 0000000000..edbfebffc5
--- /dev/null
+++ b/tests/PHPStan/Analyser/data/bug-9985.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace Bug9985;
+
+use function PHPStan\Testing\assertType;
+
+function (): void {
+	$warnings = [];
+
+	if (rand(0, 100) >= 1) {
+		$warnings['a'] = true;
+	}
+
+	if (rand(0, 100) >= 2) {
+		$warnings['b'] = true;
+	} elseif (rand(0, 100) >= 3) {
+		$warnings['c'] = true;
+	}
+
+	assertType('array{}|array{a?: true, b: true}|array{a?: true, c?: true}', $warnings);
+
+	if (!empty($warnings)) {
+		assertType('array{a?: true, b: true}|(array{a?: true, c?: true}&non-empty-array)', $warnings);
+	}
+};
diff --git a/tests/PHPStan/Type/TypeCombinatorTest.php b/tests/PHPStan/Type/TypeCombinatorTest.php
index ff1b961f90..b679b777fb 100644
--- a/tests/PHPStan/Type/TypeCombinatorTest.php
+++ b/tests/PHPStan/Type/TypeCombinatorTest.php
@@ -2450,6 +2450,50 @@ public function dataUnion(): iterable
 			NeverType::class,
 			'*NEVER*',
 		];
+		yield [
+			[
+				new ConstantArrayType([
+					new ConstantStringType('a'),
+					new ConstantStringType('b'),
+				], [
+					new ConstantBooleanType(true),
+					new ConstantBooleanType(true),
+				], [0], [0]),
+				new ConstantArrayType([
+					new ConstantStringType('a'),
+					new ConstantStringType('c'),
+				], [
+					new ConstantBooleanType(true),
+					new ConstantBooleanType(true),
+				], [0], [0, 1]),
+			],
+			UnionType::class,
+			'array{a?: true, b: true}|array{a?: true, c?: true}',
+		];
+
+		yield [
+			[
+				new ConstantArrayType([
+					new ConstantStringType('a'),
+					new ConstantStringType('b'),
+				], [
+					new ConstantBooleanType(true),
+					new ConstantBooleanType(true),
+				], [0], [0]),
+				new IntersectionType([
+					new ConstantArrayType([
+						new ConstantStringType('a'),
+						new ConstantStringType('c'),
+					], [
+						new ConstantBooleanType(true),
+						new ConstantBooleanType(true),
+					], [0], [0, 1]),
+					new NonEmptyArrayType(),
+				]),
+			],
+			UnionType::class,
+			'array{a?: true, b: true}|(array{a?: true, c?: true}&non-empty-array)',
+		];
 	}
 
 	/**
@@ -4030,6 +4074,66 @@ public function dataIntersect(): iterable
 			NonAcceptingNeverType::class,
 			'never=explicit',
 		];
+		yield [
+			[
+				new UnionType([
+					new ConstantArrayType([], []),
+					new ConstantArrayType([
+						new ConstantStringType('a'),
+						new ConstantStringType('b'),
+					], [
+						new ConstantBooleanType(true),
+						new ConstantBooleanType(true),
+					], [0], [0]),
+					new ConstantArrayType([
+						new ConstantStringType('a'),
+						new ConstantStringType('c'),
+					], [
+						new ConstantBooleanType(true),
+						new ConstantBooleanType(true),
+					], [0], [0, 1]),
+				]),
+				new NonEmptyArrayType(),
+			],
+			UnionType::class,
+			'array{a?: true, b: true}|(array{a?: true, c?: true}&non-empty-array)',
+		];
+		yield [
+			[
+				new ConstantArrayType([], []),
+				new NonEmptyArrayType(),
+			],
+			NeverType::class,
+			'*NEVER*=implicit',
+		];
+		yield [
+			[
+				new ConstantArrayType([
+					new ConstantStringType('a'),
+					new ConstantStringType('b'),
+				], [
+					new ConstantBooleanType(true),
+					new ConstantBooleanType(true),
+				], [0], [0]),
+				new NonEmptyArrayType(),
+			],
+			ConstantArrayType::class,
+			'array{a?: true, b: true}',
+		];
+		yield [
+			[
+				new ConstantArrayType([
+					new ConstantStringType('a'),
+					new ConstantStringType('c'),
+				], [
+					new ConstantBooleanType(true),
+					new ConstantBooleanType(true),
+				], [0], [0, 1]),
+				new NonEmptyArrayType(),
+			],
+			IntersectionType::class,
+			'array{a?: true, c?: true}&non-empty-array',
+		];
 	}
 
 	/**