diff --git a/libraries/tools/kotlin-main-kts-test/test/org/jetbrains/kotlin/mainKts/test/mainKtsIT.kt b/libraries/tools/kotlin-main-kts-test/test/org/jetbrains/kotlin/mainKts/test/mainKtsIT.kt
index b9b43928f06..51f66dd0369 100644
--- a/libraries/tools/kotlin-main-kts-test/test/org/jetbrains/kotlin/mainKts/test/mainKtsIT.kt
+++ b/libraries/tools/kotlin-main-kts-test/test/org/jetbrains/kotlin/mainKts/test/mainKtsIT.kt
@@ -67,6 +67,7 @@ class mainKtsIT {
             stdoutThread.join(100)
             assertFalse("stdout thread not finished", stdoutThread.isAlive)
             assertNull(stdoutException.value)
+            stderrThread.join(100)
             assertFalse("stderr thread not finished", stderrThread.isAlive)
             assertNull(stderrException.value)
             assertEquals(expectedOutPatterns.size, processOut.size)