diff --git a/js/js.libraries/src/core/char.kt b/js/js.libraries/src/core/char.kt
index 06ab5da6a19..c55edc29039 100644
--- a/js/js.libraries/src/core/char.kt
+++ b/js/js.libraries/src/core/char.kt
@@ -19,8 +19,10 @@ package kotlin.text
 // actually \s is enough to match all whitespace, but \xA0 added because of different regexp behavior of Rhino used in Selenium tests
 public fun Char.isWhitespace(): Boolean = toString().matches("[\\s\\xA0]")
 
+@kotlin.internal.InlineOnly
 public inline fun Char.toLowerCase(): Char = asDynamic().toLowerCase()
 
+@kotlin.internal.InlineOnly
 public inline fun Char.toUpperCase(): Char = asDynamic().toUpperCase()
 
 /**
diff --git a/js/js.libraries/src/core/concurrent.kt b/js/js.libraries/src/core/concurrent.kt
index 24a322f003f..9d9e1592d17 100644
--- a/js/js.libraries/src/core/concurrent.kt
+++ b/js/js.libraries/src/core/concurrent.kt
@@ -35,4 +35,5 @@ public annotation class Volatile
 @Retention(AnnotationRetention.SOURCE)
 public annotation class Synchronized
 
+@kotlin.internal.InlineOnly
 public inline fun <R> synchronized(lock: Any, crossinline block: () -> R): R = block()
diff --git a/js/js.libraries/src/core/core.kt b/js/js.libraries/src/core/core.kt
index 8042deab886..9a8c20d2583 100644
--- a/js/js.libraries/src/core/core.kt
+++ b/js/js.libraries/src/core/core.kt
@@ -20,8 +20,10 @@ public external fun js(code: String): dynamic
 /**
  * Function corresponding to JavaScript's `typeof` operator
  */
+@kotlin.internal.InlineOnly
 public inline fun jsTypeOf(a: Any?): String = js("typeof a")
 
+@kotlin.internal.InlineOnly
 internal inline fun deleteProperty(obj: Any, property: Any) {
     js("delete obj[property]")
 }
\ No newline at end of file
diff --git a/js/js.libraries/src/core/dynamic.kt b/js/js.libraries/src/core/dynamic.kt
index 9afdd6eafcc..0a79b90beae 100644
--- a/js/js.libraries/src/core/dynamic.kt
+++ b/js/js.libraries/src/core/dynamic.kt
@@ -16,11 +16,13 @@
 
 package kotlin.js
 
+@kotlin.internal.InlineOnly
 public inline fun Any?.asDynamic(): dynamic = this
 
 /**
  * Reinterprets this value as a value of the specified type [T] without any actual type checking.
  */
+@kotlin.internal.InlineOnly
 public inline fun <T> Any?.unsafeCast(): @kotlin.internal.NoInfer T = this.asDynamic()
 
 /**
@@ -28,6 +30,7 @@ public inline fun <T> Any?.unsafeCast(): @kotlin.internal.NoInfer T = this.asDyn
  */
 @kotlin.internal.DynamicExtension
 @JsName("unsafeCastDynamic")
+@kotlin.internal.InlineOnly
 public inline fun <T> dynamic.unsafeCast(): @kotlin.internal.NoInfer T = this
 
 /**
diff --git a/js/js.libraries/src/core/string.kt b/js/js.libraries/src/core/string.kt
index 03279036331..d9519e071c0 100644
--- a/js/js.libraries/src/core/string.kt
+++ b/js/js.libraries/src/core/string.kt
@@ -2,8 +2,10 @@ package kotlin.text
 
 import kotlin.text.js.RegExp
 
+@kotlin.internal.InlineOnly
 public inline fun String.toUpperCase(): String = asDynamic().toUpperCase()
 
+@kotlin.internal.InlineOnly
 public inline fun String.toLowerCase(): String = asDynamic().toLowerCase()
 
 internal inline fun String.nativeIndexOf(str: String, fromIndex: Int): Int = asDynamic().indexOf(str, fromIndex)
@@ -14,17 +16,22 @@ internal inline fun String.nativeStartsWith(s: String, position: Int): Boolean =
 
 internal inline fun String.nativeEndsWith(s: String): Boolean = asDynamic().endsWith(s)
 
+@kotlin.internal.InlineOnly
 public inline fun String.substring(startIndex: Int): String = asDynamic().substring(startIndex)
 
+@kotlin.internal.InlineOnly
 public inline fun String.substring(startIndex: Int, endIndex: Int): String = asDynamic().substring(startIndex, endIndex)
 
+@kotlin.internal.InlineOnly
 public inline fun String.concat(str: String): String = asDynamic().concat(str)
 
+@kotlin.internal.InlineOnly
 public inline fun String.match(regex: String): Array<String> = asDynamic().match(regex)
 
 //native public fun String.trim(): String
 //TODO: String.replace to implement effective trimLeading and trimTrailing
 
+@kotlin.internal.InlineOnly
 public inline val CharSequence.size: Int get() = asDynamic().length
 
 internal inline fun String.nativeReplace(pattern: RegExp, replacement: String): String = asDynamic().replace(pattern, replacement)