diff --git a/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/SerializationFirResolveExtension.kt b/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/SerializationFirResolveExtension.kt
index 800c50eb4cf..bc809809f83 100644
--- a/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/SerializationFirResolveExtension.kt
+++ b/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/SerializationFirResolveExtension.kt
@@ -260,7 +260,7 @@ class SerializationFirResolveExtension(session: FirSession) : FirDeclarationGene
 
         if (owner.name == SerialEntityNames.SERIALIZER_CLASS_NAME && owner.typeParameterSymbols.isNotEmpty()) {
             result += createConstructor(owner, SerializationPluginKey) {
-                visibility = Visibilities.Private
+                visibility = Visibilities.Public
                 owner.typeParameterSymbols.forEachIndexed { i, typeParam ->
                     valueParameter(
                         name = Name.identifier("${SerialEntityNames.typeArgPrefix}$i"),
diff --git a/plugins/kotlinx-serialization/testData/boxIr/sealedClassMultifile.kt b/plugins/kotlinx-serialization/testData/boxIr/sealedClassMultifile.kt
new file mode 100644
index 00000000000..d554f766caf
--- /dev/null
+++ b/plugins/kotlinx-serialization/testData/boxIr/sealedClassMultifile.kt
@@ -0,0 +1,28 @@
+// TARGET_BACKEND: JVM_IR
+
+// WITH_STDLIB
+
+// FILE: a.kt
+
+import kotlinx.serialization.*
+
+@Serializable
+sealed class Base {
+    abstract val id: Long
+}
+
+// FILE: b.kt
+
+import kotlinx.serialization.*
+import kotlinx.serialization.descriptors.*
+
+@Serializable
+class DerivedOtherFile<Value>(
+    override val id: Long,
+    val value: Value
+) : Base()
+
+fun box(): String {
+    val desc = Base.serializer().descriptor.kind
+    return if (desc == PolymorphicKind.SEALED) "OK" else desc.toString()
+}
diff --git a/plugins/kotlinx-serialization/testData/codegen/Intrinsics.asm.fir.txt b/plugins/kotlinx-serialization/testData/codegen/Intrinsics.asm.fir.txt
index 4d9aa952e46..119dac4cc1b 100644
--- a/plugins/kotlinx-serialization/testData/codegen/Intrinsics.asm.fir.txt
+++ b/plugins/kotlinx-serialization/testData/codegen/Intrinsics.asm.fir.txt
@@ -5,9 +5,7 @@ public final class Box$$serializer : java/lang/Object, kotlinx/serialization/int
 
     private void <init>()
 
-    private void <init>(kotlinx.serialization.KSerializer typeSerial0)
-
-    public void <init>(kotlinx.serialization.KSerializer typeSerial0, kotlin.jvm.internal.DefaultConstructorMarker $constructor_marker)
+    public void <init>(kotlinx.serialization.KSerializer typeSerial0)
 
     public final kotlinx.serialization.KSerializer[] childSerializers()
 
diff --git a/plugins/kotlinx-serialization/testData/firMembers/classWithGenericParameters.fir.txt b/plugins/kotlinx-serialization/testData/firMembers/classWithGenericParameters.fir.txt
index 8bff876c723..3b166ea3cf4 100644
--- a/plugins/kotlinx-serialization/testData/firMembers/classWithGenericParameters.fir.txt
+++ b/plugins/kotlinx-serialization/testData/firMembers/classWithGenericParameters.fir.txt
@@ -38,7 +38,7 @@ FILE: classWithGenericParameters.kt
                 super<R|kotlin/Any|>()
             }
 
-            private constructor<T, V>(typeSerial0: R|kotlinx/serialization/KSerializer<T>|, typeSerial1: R|kotlinx/serialization/KSerializer<V>|): R|GenericBox.$serializer<T, V>|
+            public constructor<T, V>(typeSerial0: R|kotlinx/serialization/KSerializer<T>|, typeSerial1: R|kotlinx/serialization/KSerializer<V>|): R|GenericBox.$serializer<T, V>|
 
         }
 
diff --git a/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirLightTreeBlackBoxTestGenerated.java b/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirLightTreeBlackBoxTestGenerated.java
index f50cad2efa8..41297a542be 100644
--- a/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirLightTreeBlackBoxTestGenerated.java
+++ b/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirLightTreeBlackBoxTestGenerated.java
@@ -213,6 +213,12 @@ public class SerializationFirLightTreeBlackBoxTestGenerated extends AbstractSeri
             runTest("plugins/kotlinx-serialization/testData/boxIr/repeatableSerialInfo.kt");
         }
 
+        @Test
+        @TestMetadata("sealedClassMultifile.kt")
+        public void testSealedClassMultifile() throws Exception {
+            runTest("plugins/kotlinx-serialization/testData/boxIr/sealedClassMultifile.kt");
+        }
+
         @Test
         @TestMetadata("sealedInterfaces.kt")
         public void testSealedInterfaces() throws Exception {
diff --git a/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationIrBoxTestGenerated.java b/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationIrBoxTestGenerated.java
index 509b3d6af41..1bdd3359aef 100644
--- a/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationIrBoxTestGenerated.java
+++ b/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationIrBoxTestGenerated.java
@@ -211,6 +211,12 @@ public class SerializationIrBoxTestGenerated extends AbstractSerializationIrBoxT
         runTest("plugins/kotlinx-serialization/testData/boxIr/repeatableSerialInfo.kt");
     }
 
+    @Test
+    @TestMetadata("sealedClassMultifile.kt")
+    public void testSealedClassMultifile() throws Exception {
+        runTest("plugins/kotlinx-serialization/testData/boxIr/sealedClassMultifile.kt");
+    }
+
     @Test
     @TestMetadata("sealedInterfaces.kt")
     public void testSealedInterfaces() throws Exception {