diff --git a/src/Type/ArrayType.php b/src/Type/ArrayType.php
index a951f13c24..2533267f6e 100644
--- a/src/Type/ArrayType.php
+++ b/src/Type/ArrayType.php
@@ -478,6 +478,12 @@ public function unsetOffset(Type $offsetType): Type
 	public function fillKeysArray(Type $valueType): Type
 	{
 		$itemType = $this->getItemType();
+		$arrayKeyType = $itemType->toArrayKey();
+
+		if ($arrayKeyType->isInteger()->yes()) {
+			return new ArrayType($arrayKeyType, $valueType);
+		}
+
 		if ($itemType->isInteger()->no()) {
 			$stringKeyType = $itemType->toString();
 			if ($stringKeyType instanceof ErrorType) {
diff --git a/tests/PHPStan/Analyser/nsrt/array-fill-keys.php b/tests/PHPStan/Analyser/nsrt/array-fill-keys.php
index 231b2dcbe5..eab3ab5da2 100644
--- a/tests/PHPStan/Analyser/nsrt/array-fill-keys.php
+++ b/tests/PHPStan/Analyser/nsrt/array-fill-keys.php
@@ -85,16 +85,20 @@ function withOptionalKeys(): void
  * @param array<int, int|string|bool> $mixed
  * @param list<string> $list
  * @param Baz[] $objectsWithoutToString
+ * @param array<int|decimal-int-string> $decimalIntStringOrInt
+ * @param array<decimal-int-string> $decimalIntString
  */
-function withNotConstantArray(array $foo, array $bar, array $baz, array $floats, array $mixed, array $list, array $objectsWithoutToString): void
+function withNotConstantArray(array $foo, array $bar, array $baz, array $floats, array $mixed, array $list, array $objectsWithoutToString, array $decimalIntStringOrInt, array $decimalIntString): void
 {
 	assertType("array<string, null>", array_fill_keys($foo, null));
 	assertType("array<int, null>", array_fill_keys($bar, null));
 	assertType("array<'foo', null>", array_fill_keys($baz, null));
-	assertType("array<numeric-string&uppercase-string, null>", array_fill_keys($floats, null));
+	assertType("array<int, null>", array_fill_keys($floats, null));
 	assertType("array<bool|int|string, null>", array_fill_keys($mixed, null));
 	assertType('array<string, null>', array_fill_keys($list, null));
 	assertType('*ERROR*', array_fill_keys($objectsWithoutToString, null));
+	assertType('array<int, null>', array_fill_keys($decimalIntStringOrInt, null));
+	assertType('array<int, null>', array_fill_keys($decimalIntString, null));
 
 	if (array_key_exists(17, $mixed)) {
 		assertType('non-empty-array<bool|int|string, null>', array_fill_keys($mixed, null));