diff --git a/libraries/stdlib/src/kotlin/time/ExperimentalTime.kt b/libraries/stdlib/src/kotlin/time/ExperimentalTime.kt
index df107a58955..7b657c82c27 100644
--- a/libraries/stdlib/src/kotlin/time/ExperimentalTime.kt
+++ b/libraries/stdlib/src/kotlin/time/ExperimentalTime.kt
@@ -19,6 +19,7 @@ import kotlin.annotation.AnnotationTarget.*
  * or by using the compiler argument `-Xuse-experimental=kotlin.time.ExperimentalTime`.
  */
 @Experimental(level = Experimental.Level.ERROR)
+@MustBeDocumented
 @Retention(AnnotationRetention.BINARY)
 @Target(
     CLASS,