diff --git a/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/KotlinJsCompilation.kt b/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/KotlinJsCompilation.kt
index 1a99d6242f8..2c2361de6cf 100644
--- a/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/KotlinJsCompilation.kt
+++ b/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/KotlinJsCompilation.kt
@@ -34,7 +34,7 @@ open class KotlinJsCompilation(
 
     override val defaultSourceSetName: String
         get() = lowerCamelCaseName(
-            target.disambiguationClassifier?.removePrefix(LEGACY_DISAMBIGUATION_CLASSIFIER)?.toLowerCase(),
+            target.disambiguationClassifier?.removePrefix(LEGACY_DISAMBIGUATION_CLASSIFIER),
             compilationName
         )
 }
\ No newline at end of file
diff --git a/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/KotlinJsTargetPreset.kt b/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/KotlinJsTargetPreset.kt
index 4dce75eeb6b..56d3c02f5cc 100644
--- a/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/KotlinJsTargetPreset.kt
+++ b/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/KotlinJsTargetPreset.kt
@@ -15,7 +15,6 @@ import org.jetbrains.kotlin.gradle.targets.js.KotlinJsTargetConfigurator
 import org.jetbrains.kotlin.gradle.targets.js.ir.KotlinJsIrSingleTargetPreset
 import org.jetbrains.kotlin.gradle.targets.js.ir.KotlinJsIrTargetConfigurator
 import org.jetbrains.kotlin.gradle.targets.js.ir.KotlinJsIrTargetPreset
-import org.jetbrains.kotlin.gradle.utils.lowerCamelCaseName
 
 open class KotlinJsTargetPreset(
     project: Project,
@@ -45,10 +44,8 @@ open class KotlinJsTargetPreset(
         if (irPreset == null) {
             super.provideTargetDisambiguationClassifier(target)
         } else {
-            lowerCamelCaseName(
-                LEGACY_DISAMBIGUATION_CLASSIFIER,
-                super.provideTargetDisambiguationClassifier(target)
-            )
+            LEGACY_DISAMBIGUATION_CLASSIFIER +
+                    super.provideTargetDisambiguationClassifier(target)
         }
 
     override fun createKotlinTargetConfigurator() = KotlinJsTargetConfigurator(