diff --git a/runtime/src/main/kotlin/kotlin/native/Compatibility.kt b/runtime/src/main/kotlin/kotlin/native/Compatibility.kt
index 9e6cfd4ea82..2a9185347b1 100644
--- a/runtime/src/main/kotlin/kotlin/native/Compatibility.kt
+++ b/runtime/src/main/kotlin/kotlin/native/Compatibility.kt
@@ -18,4 +18,5 @@ public annotation class Volatile
 public annotation class Synchronized
 
 @kotlin.internal.InlineOnly
-public actual inline fun <R> synchronized(@Suppress("UNUSED_PARAMETER") lock: Any, block: () -> R): R = block()
\ No newline at end of file
+public actual inline fun <R> synchronized(@Suppress("UNUSED_PARAMETER") lock: Any, block: () -> R): R =
+        throw UnsupportedOperationException("synchronized() is unsupported")
\ No newline at end of file
diff --git a/runtime/src/main/kotlin/kotlin/native/concurrent/Internal.kt b/runtime/src/main/kotlin/kotlin/native/concurrent/Internal.kt
index 4dcf63b3a74..bf682ec4e5d 100644
--- a/runtime/src/main/kotlin/kotlin/native/concurrent/Internal.kt
+++ b/runtime/src/main/kotlin/kotlin/native/concurrent/Internal.kt
@@ -68,7 +68,13 @@ internal fun ThrowFreezingException(toFreeze: Any, blocker: Any): Nothing =
         throw FreezingException(toFreeze, blocker)
 
 @ExportForCppRuntime
-internal fun ThrowInvalidMutabilityException(where: Any): Nothing = throw InvalidMutabilityException(where)
+internal fun ThrowInvalidMutabilityException(where: Any): Nothing {
+    val kClass = where::class
+    val className = kClass.qualifiedName ?: kClass.simpleName ?: "<object>"
+    val unsignedHashCode = where.hashCode().toLong() and 0xffffffffL
+    val hashCodeStr = unsignedHashCode.toString(16)
+    throw InvalidMutabilityException("$className@$hashCodeStr")
+}
 
 @SymbolName("Kotlin_AtomicReference_checkIfFrozen")
 external internal fun checkIfFrozen(ref: Any?)