diff --git a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/GeneratorHelpers.kt b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/GeneratorHelpers.kt
index 2c32d3c88ab..79512a16468 100644
--- a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/GeneratorHelpers.kt
+++ b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/GeneratorHelpers.kt
@@ -726,7 +726,7 @@ interface IrBuilderExtension {
 
     private fun IrConstructor.isSerializationCtor(): Boolean {
         val serialMarker =
-            compilerContext.referenceClass(SerializationPackages.packageFqName.child(SerialEntityNames.SERIAL_CTOR_MARKER_NAME))
+            compilerContext.referenceClass(SerializationPackages.internalPackageFqName.child(SerialEntityNames.SERIAL_CTOR_MARKER_NAME))
 
         return valueParameters.lastOrNull()?.run {
             name == SerialEntityNames.dummyParamName && type.classifierOrNull == serialMarker
diff --git a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/jvm/JVMCodegenUtil.kt b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/jvm/JVMCodegenUtil.kt
index 966cd95aaeb..ca2a9460824 100644
--- a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/jvm/JVMCodegenUtil.kt
+++ b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/jvm/JVMCodegenUtil.kt
@@ -126,7 +126,7 @@ internal fun InstructionAdapter.buildInternalConstructorDesc(
         load(propVar, propertyType)
         propVar += propertyType.size
     }
-    constructorDesc.append("Lkotlinx/serialization/$SERIAL_CTOR_MARKER_NAME;)V")
+    constructorDesc.append("Lkotlinx/serialization/internal/$SERIAL_CTOR_MARKER_NAME;)V")
     aconst(null)
     return constructorDesc.toString()
 }
@@ -373,7 +373,7 @@ internal fun AbstractSerialGenerator.stackValueSerializerInstance(codegen: Class
 
 fun InstructionAdapter.wrapStackValueIntoNullableSerializer() =
     invokestatic(
-        "kotlinx/serialization/internal/NullableSerializerKt", "makeNullable",
+        "kotlinx/serialization/builtins/BuiltinSerializersKt", "getNullable",
         "(" + kSerializerType.descriptor + ")" + kSerializerType.descriptor, false
     )
 
diff --git a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/NamingConventions.kt b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/NamingConventions.kt
index 9585e23ea65..29cfbe3d6e4 100644
--- a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/NamingConventions.kt
+++ b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/NamingConventions.kt
@@ -59,7 +59,7 @@ object SerialEntityNames {
     const val SERIAL_LOADER_CLASS = "DeserializationStrategy"
 
     const val SERIAL_DESCRIPTOR_CLASS = "SerialDescriptor"
-    const val SERIAL_DESCRIPTOR_CLASS_IMPL = "SerialClassDescImpl"
+    const val SERIAL_DESCRIPTOR_CLASS_IMPL = "PluginGeneratedSerialDescriptor"
     const val SERIAL_DESCRIPTOR_FOR_ENUM = "EnumDescriptor"
 
     //exceptions
diff --git a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/SearchUtils.kt b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/SearchUtils.kt
index 948a28bcc10..497d1e9d3d2 100644
--- a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/SearchUtils.kt
+++ b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/SearchUtils.kt
@@ -1,6 +1,6 @@
 /*
- * Copyright 2010-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
- * that can be found in the license/LICENSE.txt file.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
 package org.jetbrains.kotlinx.serialization.compiler.resolve
@@ -23,7 +23,7 @@ internal fun ClassConstructorDescriptor.isSerializationCtor(): Boolean {
     /*kind == CallableMemberDescriptor.Kind.SYNTHESIZED does not work because DeserializedClassConstructorDescriptor loses its kind*/
     return valueParameters.lastOrNull()?.run {
         name == SerialEntityNames.dummyParamName && type.constructor.declarationDescriptor?.classId == ClassId(
-            SerializationPackages.packageFqName,
+            SerializationPackages.internalPackageFqName,
             SerialEntityNames.SERIAL_CTOR_MARKER_NAME
         )
     } == true
@@ -61,7 +61,12 @@ internal fun Annotations.findAnnotationKotlinTypeValue(
     }
 
 internal fun ClassDescriptor.getKSerializerConstructorMarker(): ClassDescriptor =
-    module.findClassAcrossModuleDependencies(ClassId(SerializationPackages.packageFqName, SerialEntityNames.SERIAL_CTOR_MARKER_NAME))!!
+    module.findClassAcrossModuleDependencies(
+        ClassId(
+            SerializationPackages.internalPackageFqName,
+            SerialEntityNames.SERIAL_CTOR_MARKER_NAME
+        )
+    )!!
 
 internal fun getInternalPackageFqn(classSimpleName: String): FqName =
     SerializationPackages.internalPackageFqName.child(Name.identifier(classSimpleName))