diff --git a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/Context.kt b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/Context.kt
index cb57f181512..6051c8fbbdd 100644
--- a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/Context.kt
+++ b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/Context.kt
@@ -71,6 +71,7 @@ internal class SpecialDescriptorsFactory(val context: Context) {
 
         bridgeDescriptor.initialize(
                 extensionReceiverType,
+                // TODO: bug in descriptor - https://youtrack.jetbrains.com/issue/KT-16438.
                 (descriptor.containingDeclaration as ClassDescriptor).thisAsReceiverParameter,
                 descriptor.typeParameters,
                 descriptor.valueParameters.mapIndexed { index, valueParameterDescriptor ->
diff --git a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/descriptors/DescriptorUtils.kt b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/descriptors/DescriptorUtils.kt
index c40e23e30a1..7929c7649a5 100644
--- a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/descriptors/DescriptorUtils.kt
+++ b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/descriptors/DescriptorUtils.kt
@@ -240,13 +240,15 @@ internal class BridgeDirections(val array: Array<BridgeDirection>) {
     fun allNotNeeded(): Boolean = array.all { it == BridgeDirection.NOT_NEEDED }
 
     override fun toString(): String {
-        return String(array.map {
-            when (it) {
+        val result = StringBuilder()
+        array.forEach {
+            result.append(when (it) {
                 BridgeDirection.FROM_VALUE_TYPE -> 'U' // unbox
                 BridgeDirection.TO_VALUE_TYPE -> 'B' // box
                 BridgeDirection.NOT_NEEDED -> 'N' // none
-            }
-        }.toCharArray())
+            })
+        }
+        return result.toString()
     }
 
     override fun equals(other: Any?): Boolean {