diff --git a/idea/testData/multiModuleHighlighting/multiplatform/basic/common/common.kt b/idea/testData/multiModuleHighlighting/multiplatform/basic/common/common.kt
index 9cd65939cd1..bb08bd6c2c4 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/basic/common/common.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/basic/common/common.kt
@@ -1,3 +1,3 @@
-header class <error descr="[HEADER_WITHOUT_IMPLEMENTATION] 'header' class 'My' has no implementation in module jvm for JVM">My</error> {
+expect class <error descr="[HEADER_WITHOUT_IMPLEMENTATION] 'header' class 'My' has no implementation in module jvm for JVM">My</error> {
 
 }
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/basic/jvm/jvm.kt b/idea/testData/multiModuleHighlighting/multiplatform/basic/jvm/jvm.kt
index 6a231197d92..a11a7b7cda4 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/basic/jvm/jvm.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/basic/jvm/jvm.kt
@@ -1,15 +1,15 @@
-impl class <error descr="[IMPLEMENTATION_WITHOUT_HEADER] 'impl' class 'Your' has no corresponding 'header' declaration">Your</error> {
+actual class <error descr="[IMPLEMENTATION_WITHOUT_HEADER] 'impl' class 'Your' has no corresponding 'header' declaration">Your</error> {
 
 }
 
-header class <error descr="[HEADER_WITHOUT_IMPLEMENTATION] 'header' class 'His' has no implementation in module jvm for JVM">His</error> {
+expect class <error descr="[HEADER_WITHOUT_IMPLEMENTATION] 'header' class 'His' has no implementation in module jvm for JVM">His</error> {
 
 }
 
-header class Their {
+expect class Their {
 
 }
 
-impl class Their {
+actual class Their {
 
 }
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/headerClass/common/common.kt b/idea/testData/multiModuleHighlighting/multiplatform/headerClass/common/common.kt
index 9a0bb2aa597..d0031a5ddea 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/headerClass/common/common.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/headerClass/common/common.kt
@@ -1,3 +1,3 @@
-header class My {
+expect class My {
 
 }
\ No newline at end of file
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/headerClass/jvm/jvm.kt b/idea/testData/multiModuleHighlighting/multiplatform/headerClass/jvm/jvm.kt
index 35e530f7c43..7f9d074b933 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/headerClass/jvm/jvm.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/headerClass/jvm/jvm.kt
@@ -1,3 +1,3 @@
-impl class My {
+actual class My {
 
 }
\ No newline at end of file
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/headerClassImplTypealias/common/common.kt b/idea/testData/multiModuleHighlighting/multiplatform/headerClassImplTypealias/common/common.kt
index eae393da3ea..8994d44b0c6 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/headerClassImplTypealias/common/common.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/headerClassImplTypealias/common/common.kt
@@ -1,7 +1,7 @@
 package test
 
-header class Simple
-header fun createSimple(): Simple
+expect class Simple
+expect fun createSimple(): Simple
 
-header class Generic<A, B>
-header fun <A, B> createGeneric(a: A, b: B): Generic<A, B>
+expect class Generic<A, B>
+expect fun <A, B> createGeneric(a: A, b: B): Generic<A, B>
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/headerClassImplTypealias/jvm/jvm.kt b/idea/testData/multiModuleHighlighting/multiplatform/headerClassImplTypealias/jvm/jvm.kt
index 2572c97fbfe..bc0d31ac6b4 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/headerClassImplTypealias/jvm/jvm.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/headerClassImplTypealias/jvm/jvm.kt
@@ -1,9 +1,9 @@
 package test
 
 class SimpleImpl
-impl typealias Simple = SimpleImpl
-impl fun createSimple(): Simple = SimpleImpl()
+actual typealias Simple = SimpleImpl
+actual fun createSimple(): Simple = SimpleImpl()
 
 class GenericImpl<A, B>
-impl typealias Generic<A, B> = GenericImpl<A, B>
-impl fun <A, B> createGeneric(a: A, b: B): Generic<A, B> = GenericImpl()
+actual typealias Generic<A, B> = GenericImpl<A, B>
+actual fun <A, B> createGeneric(a: A, b: B): Generic<A, B> = GenericImpl()
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/headerFunUsesStdlibInSignature/common/common.kt b/idea/testData/multiModuleHighlighting/multiplatform/headerFunUsesStdlibInSignature/common/common.kt
index 678068289aa..68e356d2506 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/headerFunUsesStdlibInSignature/common/common.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/headerFunUsesStdlibInSignature/common/common.kt
@@ -1,11 +1,11 @@
 package test
 
-header fun stringBuilder(sb: StringBuilder)
+expect fun stringBuilder(sb: StringBuilder)
 
-header fun kotlinVersion(kv: KotlinVersion)
+expect fun kotlinVersion(kv: KotlinVersion)
 
-header fun regex(r: Regex)
+expect fun regex(r: Regex)
 
-header fun pair(p: Pair<String, List<Double>>)
+expect fun pair(p: Pair<String, List<Double>>)
 
-header fun <A, B> genericPair(p: Pair<A, B>)
+expect fun <A, B> genericPair(p: Pair<A, B>)
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/headerFunUsesStdlibInSignature/jvm/jvm.kt b/idea/testData/multiModuleHighlighting/multiplatform/headerFunUsesStdlibInSignature/jvm/jvm.kt
index 40f295d60c1..25c927ec833 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/headerFunUsesStdlibInSignature/jvm/jvm.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/headerFunUsesStdlibInSignature/jvm/jvm.kt
@@ -1,11 +1,11 @@
 package test
 
-impl fun stringBuilder(sb: StringBuilder) {}
+actual fun stringBuilder(sb: StringBuilder) {}
 
-impl fun kotlinVersion(kv: KotlinVersion) {}
+actual fun kotlinVersion(kv: KotlinVersion) {}
 
-impl fun regex(r: Regex) {}
+actual fun regex(r: Regex) {}
 
-impl fun pair(p: Pair<String, List<Double>>) {}
+actual fun pair(p: Pair<String, List<Double>>) {}
 
-impl fun <A, B> genericPair(p: Pair<A, B>) {}
+actual fun <A, B> genericPair(p: Pair<A, B>) {}
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/headerFunctionProperty/common/common.kt b/idea/testData/multiModuleHighlighting/multiplatform/headerFunctionProperty/common/common.kt
index 0d722e2ac8c..7f9fe09fbe6 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/headerFunctionProperty/common/common.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/headerFunctionProperty/common/common.kt
@@ -1,3 +1,3 @@
-header fun foo(): Int
+expect fun foo(): Int
 
-header val bar: String
+expect val bar: String
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/headerFunctionProperty/jvm/jvm.kt b/idea/testData/multiModuleHighlighting/multiplatform/headerFunctionProperty/jvm/jvm.kt
index a5469a051df..c280369f293 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/headerFunctionProperty/jvm/jvm.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/headerFunctionProperty/jvm/jvm.kt
@@ -1,3 +1,3 @@
-impl fun foo() = 42
+actual fun foo() = 42
 
-impl val bar = "Hello"
+actual val bar = "Hello"
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/headerPartiallyImplemented/common/common.kt b/idea/testData/multiModuleHighlighting/multiplatform/headerPartiallyImplemented/common/common.kt
index 711948dbd23..9b6a2eb04f8 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/headerPartiallyImplemented/common/common.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/headerPartiallyImplemented/common/common.kt
@@ -1,4 +1,4 @@
-header class My {
+expect class My {
 
     fun foo(): Int
 
@@ -6,7 +6,7 @@ header class My {
 
 }
 
-header class Your {
+expect class Your {
 
     fun foo(): Int
 
@@ -14,7 +14,7 @@ header class Your {
 
 }
 
-header class His {
+expect class His {
 
     fun foo(): Int
 
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/headerPartiallyImplemented/jvm/jvm.kt b/idea/testData/multiModuleHighlighting/multiplatform/headerPartiallyImplemented/jvm/jvm.kt
index 814c97b38a0..bd395c41646 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/headerPartiallyImplemented/jvm/jvm.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/headerPartiallyImplemented/jvm/jvm.kt
@@ -1,20 +1,20 @@
-impl class <error>My</error> {
+actual class <error>My</error> {
 
-    impl fun foo() = 42
+    actual fun foo() = 42
 }
 
-impl class Your {
+actual class Your {
 
-    impl fun foo() = 13
+    actual fun foo() = 13
 
-    <error>impl fun bar(arg: Int)</error> = arg
+    <error>actual fun bar(arg: Int)</error> = arg
 
 }
 
-impl class His {
+actual class His {
 
-    impl fun foo() = 7
+    actual fun foo() = 7
 
-    impl fun bar(arg: Int) = arg == foo()
+    actual fun bar(arg: Int) = arg == foo()
 
 }
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/headerWithoutImplForBoth/common/common.kt b/idea/testData/multiModuleHighlighting/multiplatform/headerWithoutImplForBoth/common/common.kt
index 49b31b7f1c4..fd24b7b6c0d 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/headerWithoutImplForBoth/common/common.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/headerWithoutImplForBoth/common/common.kt
@@ -1,3 +1,3 @@
-header class <error descr="[HEADER_WITHOUT_IMPLEMENTATION] 'header' class 'My' has no implementation in module js for JS"><error descr="[HEADER_WITHOUT_IMPLEMENTATION] 'header' class 'My' has no implementation in module jvm for JVM">My</error></error> {
+expect class <error descr="[HEADER_WITHOUT_IMPLEMENTATION] 'header' class 'My' has no implementation in module js for JS"><error descr="[HEADER_WITHOUT_IMPLEMENTATION] 'header' class 'My' has no implementation in module jvm for JVM">My</error></error> {
 
 }
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/nestedClassWithoutImpl/common/common.kt b/idea/testData/multiModuleHighlighting/multiplatform/nestedClassWithoutImpl/common/common.kt
index 595768499b6..6b57aa56910 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/nestedClassWithoutImpl/common/common.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/nestedClassWithoutImpl/common/common.kt
@@ -1,15 +1,15 @@
 package a
 
-header class A {
+expect class A {
     class Nested
 }
 
-header class B {
+expect class B {
     class Nested {
         fun foo(s: String)
     }
 }
 
-header class C {
+expect class C {
     <error>header</error> inner class Inner
 }
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/nestedClassWithoutImpl/jvm/jvm.kt b/idea/testData/multiModuleHighlighting/multiplatform/nestedClassWithoutImpl/jvm/jvm.kt
index 092dc9c8c56..f08648f8d5b 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/nestedClassWithoutImpl/jvm/jvm.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/nestedClassWithoutImpl/jvm/jvm.kt
@@ -1,11 +1,11 @@
 package a
 
-impl class <error>A</error>
+actual class <error>A</error>
 
-impl class B {
-    impl class <error>Nested</error>
+actual class B {
+    actual class <error>Nested</error>
 }
 
-impl class C {
-    impl inner class Inner
+actual class C {
+    actual inner class Inner
 }
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/suppressHeaderWithoutImpl/common/common.kt b/idea/testData/multiModuleHighlighting/multiplatform/suppressHeaderWithoutImpl/common/common.kt
index f254d5bcc61..5a5231ba567 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/suppressHeaderWithoutImpl/common/common.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/suppressHeaderWithoutImpl/common/common.kt
@@ -1,7 +1,7 @@
 // See KT-15601
 
 @Suppress("HEADER_WITHOUT_IMPLEMENTATION")
-header interface Event
+expect interface Event
 
 @Suppress("SOMETHING_WRONG")
-header class <error descr="[HEADER_WITHOUT_IMPLEMENTATION] 'header' class 'Wrong' has no implementation in module jvm for JVM">Wrong</error>
+expect class <error descr="[HEADER_WITHOUT_IMPLEMENTATION] 'header' class 'Wrong' has no implementation in module jvm for JVM">Wrong</error>
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/withOverrides/common/common.kt b/idea/testData/multiModuleHighlighting/multiplatform/withOverrides/common/common.kt
index 9f0391e725b..c47433ce93d 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/withOverrides/common/common.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/withOverrides/common/common.kt
@@ -1,3 +1,3 @@
-header fun foo(arg: Int): Int
+expect fun foo(arg: Int): Int
 
-<error>header fun foo(): Int</error>
+<error>expect fun foo(): Int</error>
diff --git a/idea/testData/multiModuleHighlighting/multiplatform/withOverrides/jvm/jvm.kt b/idea/testData/multiModuleHighlighting/multiplatform/withOverrides/jvm/jvm.kt
index 1922060a08b..c6402a209ac 100644
--- a/idea/testData/multiModuleHighlighting/multiplatform/withOverrides/jvm/jvm.kt
+++ b/idea/testData/multiModuleHighlighting/multiplatform/withOverrides/jvm/jvm.kt
@@ -1 +1 @@
-impl fun foo(arg: Int) = arg
\ No newline at end of file
+actual fun foo(arg: Int) = arg
\ No newline at end of file