diff --git a/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
index 40ed2b3f2f4..2163902ba14 100755
--- a/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -1311,7 +1311,7 @@ function simpletest_script_reporter_write_xml_results() {
 function simpletest_script_reporter_timer_stop() {
   echo "\n";
   $end = Timer::stop('run-tests');
-  echo "Test run duration: " . \Drupal::service('date.formatter')->formatInterval($end['time'] / 1000);
+  echo "Test run duration: " . \Drupal::service('date.formatter')->formatInterval((int) ($end['time'] / 1000));
   echo "\n\n";
 }