diff --git a/src/Utils/Strings.php b/src/Utils/Strings.php
index 77553a56f..958823d1e 100644
--- a/src/Utils/Strings.php
+++ b/src/Utils/Strings.php
@@ -456,6 +456,8 @@ private static function pos(string $haystack, string $needle, int $nth = 1): ?in
 			$len = strlen($haystack);
 			if ($needle === '') {
 				return $len;
+			} elseif ($len === 0) {
+				return null;
 			}
 			$pos = $len - 1;
 			while (($pos = strrpos($haystack, $needle, $pos - $len)) !== false && ++$nth) {
diff --git a/tests/Utils/Strings.indexOf().phpt b/tests/Utils/Strings.indexOf().phpt
index b89113813..5a89e7bc6 100644
--- a/tests/Utils/Strings.indexOf().phpt
+++ b/tests/Utils/Strings.indexOf().phpt
@@ -31,6 +31,8 @@ test('', function () {
 	Assert::null(Strings::indexOf($foo, 'not-in-string'));
 	Assert::null(Strings::indexOf($foo, 'b', -2));
 	Assert::null(Strings::indexOf($foo, 'b', 2));
+	Assert::null(Strings::indexOf('', 'a', 1));
+	Assert::null(Strings::indexOf('', 'a', -1));
 });