diff --git a/src/Type/Php/ArrayKeyExistsFunctionTypeSpecifyingExtension.php b/src/Type/Php/ArrayKeyExistsFunctionTypeSpecifyingExtension.php
index ffbdc4069f..c48fee653f 100644
--- a/src/Type/Php/ArrayKeyExistsFunctionTypeSpecifyingExtension.php
+++ b/src/Type/Php/ArrayKeyExistsFunctionTypeSpecifyingExtension.php
@@ -77,17 +77,15 @@ public function specifyTypes(
 			if ($context->true()) {
 				$specifiedTypes = new SpecifiedTypes();
 
-				if (count($keyType->getConstantScalarTypes()) <= 1) {
-					$nonEmptyType = $arrayType->isArray()->yes()
-						? new NonEmptyArrayType()
-						: TypeCombinator::intersect(new ArrayType(new MixedType(), new MixedType()), new NonEmptyArrayType());
-					$specifiedTypes = $specifiedTypes->unionWith($this->typeSpecifier->create(
-						$array,
-						$nonEmptyType,
-						$context,
-						$scope,
-					));
-				}
+				$nonEmptyType = $arrayType->isArray()->yes()
+					? new NonEmptyArrayType()
+					: TypeCombinator::intersect(new ArrayType(new MixedType(), new MixedType()), new NonEmptyArrayType());
+				$specifiedTypes = $specifiedTypes->unionWith($this->typeSpecifier->create(
+					$array,
+					$nonEmptyType,
+					$context,
+					$scope,
+				));
 
 				if ($arrayType->isIterableAtLeastOnce()->no()) {
 					return $specifiedTypes;
diff --git a/tests/PHPStan/Analyser/nsrt/bug-14489.php b/tests/PHPStan/Analyser/nsrt/bug-14489.php
new file mode 100644
index 0000000000..58f8d17b71
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-14489.php
@@ -0,0 +1,46 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14489;
+
+use function array_key_exists;
+use function array_merge;
+use function array_unique;
+use function array_values;
+use function PHPStan\Testing\assertType;
+
+function () {
+	$data = [['c1' => [1], 'c2' => [4]]];
+
+	$cData = [];
+	foreach ($data as $cMap) {
+		foreach ($cMap as $c => $ids) {
+			if (array_key_exists($c, $cData)) {
+				$cData[$c] = array_unique(array_merge($cData[$c], $ids));
+			} else {
+				$cData[$c] = $ids;
+			}
+		}
+	}
+
+	$values = array_values($cData);
+	assertType('non-empty-list<non-empty-array<0|1, 1|4>>', $values);
+};
+
+function () {
+	/** @var 'c1'|'c2' $c */
+	$c = 'c1';
+	/** @var array{1}|array{4} $ids */
+	$ids = [1];
+
+	$cData = [];
+	while (rand(0, 1)) {
+		if (array_key_exists($c, $cData)) {
+			assertType('non-empty-array<\'c1\'|\'c2\', array{1}|array{4}>', $cData);
+			assertType('array{1}|array{4}', $cData[$c]);
+			$cData[$c] = $cData[$c];
+		} else {
+			$cData[$c] = $ids;
+		}
+	}
+	assertType('array<\'c1\'|\'c2\', array{1}|array{4}>', $cData);
+};
diff --git a/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php b/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php
index a3a31d3948..7cd71f4123 100644
--- a/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php
+++ b/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php
@@ -419,7 +419,7 @@ public function testBug7000b(): void
 	{
 		$this->analyse([__DIR__ . '/data/bug-7000b.php'], [
 			[
-				"Offset 'require'|'require-dev' might not exist on array{require?: array<string, string>, require-dev?: array<string, string>}.",
+				"Offset 'require'|'require-dev' might not exist on non-empty-array{require?: array<string, string>, require-dev?: array<string, string>}.",
 				16,
 			],
 		]);