diff --git a/js/js.libraries/src/core/javautilCollections.kt b/js/js.libraries/src/core/javautilCollections.kt
index 4a7f3d3ffc2..cec6a639cae 100644
--- a/js/js.libraries/src/core/javautilCollections.kt
+++ b/js/js.libraries/src/core/javautilCollections.kt
@@ -4,10 +4,10 @@ import java.lang.*
 import java.util.*
 
 library("collectionsMax")
-public fun max<T>(col : Collection<T>, comp : Comparator<T>) : T = noImpl
+public fun max<T>(col : Collection<T>, comp : Comparator<in T>) : T = noImpl
 
 library("collectionsSort")
 public fun <T> sort(list: MutableList<T>): Unit = noImpl
 
 library("collectionsSort")
-public fun <T> sort(list: MutableList<T>, comparator: java.util.Comparator<T>): Unit = noImpl
+public fun <T> sort(list: MutableList<T>, comparator: java.util.Comparator<in T>): Unit = noImpl
diff --git a/libraries/stdlib/src/generated/_Ordering.kt b/libraries/stdlib/src/generated/_Ordering.kt
index 9d036833072..5137f2d602a 100644
--- a/libraries/stdlib/src/generated/_Ordering.kt
+++ b/libraries/stdlib/src/generated/_Ordering.kt
@@ -116,7 +116,7 @@ public fun <T : Comparable<T>> Iterable<T>.sort(): List<T> {
 /**
  * Returns a list of all elements, sorted by the specified *comparator*
  */
-public fun <T> Array<out T>.sortBy(comparator: Comparator<T>): List<T> {
+public fun <T> Array<out T>.sortBy(comparator: Comparator<in T>): List<T> {
     val sortedList = toArrayList()
     java.util.Collections.sort(sortedList, comparator)
     return sortedList
@@ -125,7 +125,7 @@ public fun <T> Array<out T>.sortBy(comparator: Comparator<T>): List<T> {
 /**
  * Returns a list of all elements, sorted by the specified *comparator*
  */
-public fun <T> Iterable<T>.sortBy(comparator: Comparator<T>): List<T> {
+public fun <T> Iterable<T>.sortBy(comparator: Comparator<in T>): List<T> {
     val sortedList = toArrayList()
     java.util.Collections.sort(sortedList, comparator)
     return sortedList
diff --git a/libraries/tools/kotlin-stdlib-gen/src/templates/Ordering.kt b/libraries/tools/kotlin-stdlib-gen/src/templates/Ordering.kt
index 93a390d372d..89e8e9aac7e 100644
--- a/libraries/tools/kotlin-stdlib-gen/src/templates/Ordering.kt
+++ b/libraries/tools/kotlin-stdlib-gen/src/templates/Ordering.kt
@@ -161,7 +161,7 @@ fun ordering(): List<GenericFunction> {
         exclude(Strings)
     }
 
-    templates add f("sortBy(comparator: Comparator<T>)") {
+    templates add f("sortBy(comparator: Comparator<in T>)") {
         doc {
             """
             Returns a list of all elements, sorted by the specified *comparator*