diff --git a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/IrPreGenerator.kt b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/IrPreGenerator.kt
index cebff63e5ad..09b984207c6 100644
--- a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/IrPreGenerator.kt
+++ b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/IrPreGenerator.kt
@@ -56,7 +56,7 @@ class IrPreGenerator(
             dispatchReceiverParameter = null // function is static
         }
 
-        val typeParams = serializerDescriptor.typeParameters.map {
+        val typeParams = irClass.typeParameters.map {
             method.addTypeParameter(
                 it.name.asString(), compilerContext.irBuiltIns.anyNType
             )
diff --git a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/fir/SerializationFirUtils.kt b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/fir/SerializationFirUtils.kt
index dab892a38a6..faaec7afda1 100644
--- a/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/fir/SerializationFirUtils.kt
+++ b/plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/fir/SerializationFirUtils.kt
@@ -46,7 +46,7 @@ internal val FirClassSymbol<*>.isInternallySerializableObject: Boolean
     get() = classKind == ClassKind.OBJECT && hasSerializableAnnotationWithoutArgs
 
 internal val FirClassSymbol<*>.isSealedSerializableInterface: Boolean
-    get() = classKind == ClassKind.INTERFACE && modality == Modality.SEALED && hasSerializableAnnotation
+    get() = classKind == ClassKind.INTERFACE && rawStatus.modality == Modality.SEALED && hasSerializableAnnotation
 
 internal val FirClassSymbol<*>.isInternalSerializable: Boolean
     get() {
diff --git a/plugins/kotlin-serialization/kotlin-serialization-compiler/test/org/jetbrains/kotlinx/serialization/SerializationFirBlackBoxTestGenerated.java b/plugins/kotlin-serialization/kotlin-serialization-compiler/test/org/jetbrains/kotlinx/serialization/SerializationFirBlackBoxTestGenerated.java
index 2acb1603e16..63ad7828183 100644
--- a/plugins/kotlin-serialization/kotlin-serialization-compiler/test/org/jetbrains/kotlinx/serialization/SerializationFirBlackBoxTestGenerated.java
+++ b/plugins/kotlin-serialization/kotlin-serialization-compiler/test/org/jetbrains/kotlinx/serialization/SerializationFirBlackBoxTestGenerated.java
@@ -20,6 +20,12 @@ import java.util.regex.Pattern;
 @TestMetadata("plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers")
 @TestDataPath("$PROJECT_ROOT")
 public class SerializationFirBlackBoxTestGenerated extends AbstractSerializationFirBlackBoxTest {
+    @Test
+    @TestMetadata("abstractAndSealed.kt")
+    public void testAbstractAndSealed() throws Exception {
+        runTest("plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers/abstractAndSealed.kt");
+    }
+
     @Test
     public void testAllFilesPresentInFirMembers() throws Exception {
         KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.JVM_IR, true);
diff --git a/plugins/kotlin-serialization/kotlin-serialization-compiler/test/org/jetbrains/kotlinx/serialization/SerializationFirMembersTestGenerated.java b/plugins/kotlin-serialization/kotlin-serialization-compiler/test/org/jetbrains/kotlinx/serialization/SerializationFirMembersTestGenerated.java
index ed67b2592d8..ba707c4f942 100644
--- a/plugins/kotlin-serialization/kotlin-serialization-compiler/test/org/jetbrains/kotlinx/serialization/SerializationFirMembersTestGenerated.java
+++ b/plugins/kotlin-serialization/kotlin-serialization-compiler/test/org/jetbrains/kotlinx/serialization/SerializationFirMembersTestGenerated.java
@@ -19,6 +19,12 @@ import java.util.regex.Pattern;
 @TestMetadata("plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers")
 @TestDataPath("$PROJECT_ROOT")
 public class SerializationFirMembersTestGenerated extends AbstractSerializationFirMembersTest {
+    @Test
+    @TestMetadata("abstractAndSealed.kt")
+    public void testAbstractAndSealed() throws Exception {
+        runTest("plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers/abstractAndSealed.kt");
+    }
+
     @Test
     public void testAllFilesPresentInFirMembers() throws Exception {
         KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers"), Pattern.compile("^(.+)\\.kt$"), null, true);
diff --git a/plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers/abstractAndSealed.fir.txt b/plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers/abstractAndSealed.fir.txt
new file mode 100644
index 00000000000..b7122cb08bc
--- /dev/null
+++ b/plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers/abstractAndSealed.fir.txt
@@ -0,0 +1,144 @@
+FILE: abstractAndSealed.kt
+    @R|kotlinx/serialization/Serializable|() public sealed interface I : R|kotlin/Any| {
+        public final companion object Companion : R|kotlin/Any| {
+            public final fun serializer(): R|kotlinx/serialization/KSerializer<I>|
+
+            private constructor(): R|I.Companion|
+
+        }
+
+    }
+    @R|kotlinx/serialization/Serializable|() public sealed class X : R|I| {
+        protected constructor(): R|X| {
+            super<R|kotlin/Any|>()
+        }
+
+        private final var x: R|kotlin/String| = String(X)
+            private get(): R|kotlin/String|
+            private set(value: R|kotlin/String|): R|kotlin/Unit|
+
+        public final fun exposeX(): R|kotlin/String| {
+            ^exposeX this@R|/X|.R|/X.x|
+        }
+
+        public final companion object Companion : R|kotlin/Any| {
+            public final fun serializer(): R|kotlinx/serialization/KSerializer<X>|
+
+            private constructor(): R|X.Companion|
+
+        }
+
+    }
+    @R|kotlinx/serialization/Serializable|() public abstract class Y : R|X| {
+        public constructor(): R|Y| {
+            super<R|X|>()
+        }
+
+        private final var y: R|kotlin/String| = String(Y)
+            private get(): R|kotlin/String|
+            private set(value: R|kotlin/String|): R|kotlin/Unit|
+
+        public final fun exposeY(): R|kotlin/String| {
+            ^exposeY this@R|/Y|.R|/Y.y|
+        }
+
+        public final companion object Companion : R|kotlin/Any| {
+            public final fun serializer(): R|kotlinx/serialization/KSerializer<Y>|
+
+            private constructor(): R|Y.Companion|
+
+        }
+
+    }
+    @R|kotlinx/serialization/Serializable|() public final class Bottom : R|Y| {
+        public constructor(): R|Bottom| {
+            super<R|Y|>()
+        }
+
+        public final companion object Companion : R|kotlin/Any| {
+            public final fun serializer(): R|kotlinx/serialization/KSerializer<Bottom>|
+
+            private constructor(): R|Bottom.Companion|
+
+        }
+
+        public final object $serializer : R|kotlinx/serialization/internal/GeneratedSerializer<Bottom>| {
+            public final fun serialize(encoder: R|kotlinx/serialization/encoding/Encoder|, value: R|Bottom|): R|kotlin/Unit|
+
+            public final fun deserialize(decoder: R|kotlinx/serialization/encoding/Decoder|): R|Bottom|
+
+            public final val descriptor: R|kotlinx/serialization/descriptors/SerialDescriptor|
+                public get(): R|kotlinx/serialization/descriptors/SerialDescriptor|
+
+            public final fun childSerializers(): R|kotlin/Array<kotlinx/serialization/KSerializer<*>>|
+
+            private constructor(): R|Bottom.$serializer|
+
+        }
+
+    }
+    public final fun testData(results: R|kotlin/String|): R|kotlin/String| {
+        when () {
+            !=(R|<local>/results|, String(OK)) ->  {
+                ^testData R|<local>/results|
+            }
+        }
+
+        lval serial: R|kotlinx/serialization/KSerializer<Bottom>| = Q|Bottom|.R|/Bottom.Companion.serializer|()
+        lval j: R|kotlinx/serialization/json/Json| = R|kotlinx/serialization/json/Json|(<L> = Json@fun R|kotlinx/serialization/json/JsonBuilder|.<anonymous>(): R|kotlin/Unit| <inline=NoInline>  {
+            this@R|special/anonymous|.R|kotlinx/serialization/json/JsonBuilder.encodeDefaults| = Boolean(true)
+        }
+        )
+        lval s: R|kotlin/String| = R|<local>/j|.R|kotlinx/serialization/json/Json.encodeToString|<R|Bottom|>(R|<local>/serial|, R|/Bottom.Bottom|())
+        when () {
+            !=(R|<local>/s|, String({"x":"X","y":"Y"})) ->  {
+                ^testData <strcat>(String(Incorrect encoding: ), R|<local>/s|)
+            }
+        }
+
+        lval decoded: R|Bottom| = R|<local>/j|.R|kotlinx/serialization/json/Json.decodeFromString|<R|Bottom|>(R|<local>/serial|, String({"x":"1","y":"2"}))
+        when () {
+            !=(R|<local>/decoded|.R|/X.exposeX|(), String(1)) ->  {
+                ^testData String(Incorrect X)
+            }
+        }
+
+        when () {
+            !=(R|<local>/decoded|.R|/Y.exposeY|(), String(2)) ->  {
+                ^testData String(Incorrect Y)
+            }
+        }
+
+        ^testData String(OK)
+    }
+    @R|kotlin/OptIn|(markerClass = vararg(<getClass>(Q|kotlinx/serialization/ExperimentalSerializationApi|))) public final fun testKinds(): R|kotlin/String| {
+        when () {
+            !=(Q|I|.R|/I.Companion.serializer|().R|SubstitutionOverride<kotlinx/serialization/KSerializer.descriptor: R|kotlinx/serialization/descriptors/SerialDescriptor|>|.R|kotlinx/serialization/descriptors/SerialDescriptor.kind|, Q|kotlinx/serialization/descriptors/PolymorphicKind.SEALED|) ->  {
+                ^testKinds String(Not sealed: I)
+            }
+        }
+
+        when () {
+            !=(Q|X|.R|/X.Companion.serializer|().R|SubstitutionOverride<kotlinx/serialization/KSerializer.descriptor: R|kotlinx/serialization/descriptors/SerialDescriptor|>|.R|kotlinx/serialization/descriptors/SerialDescriptor.kind|, Q|kotlinx/serialization/descriptors/PolymorphicKind.SEALED|) ->  {
+                ^testKinds String(Not sealed: X)
+            }
+        }
+
+        when () {
+            !=(Q|Y|.R|/Y.Companion.serializer|().R|SubstitutionOverride<kotlinx/serialization/KSerializer.descriptor: R|kotlinx/serialization/descriptors/SerialDescriptor|>|.R|kotlinx/serialization/descriptors/SerialDescriptor.kind|, Q|kotlinx/serialization/descriptors/PolymorphicKind.OPEN|) ->  {
+                ^testKinds String(Not polymorphic: Y)
+            }
+        }
+
+        lval serial: R|kotlinx/serialization/KSerializer<Bottom>| = Q|Bottom|.R|/Bottom.Companion.serializer|()
+        when () {
+            !=(R|<local>/serial|.R|SubstitutionOverride<kotlinx/serialization/KSerializer.descriptor: R|kotlinx/serialization/descriptors/SerialDescriptor|>|.R|kotlinx/serialization/descriptors/SerialDescriptor.kind|, Q|kotlinx/serialization/descriptors/StructureKind.CLASS|) ->  {
+                ^testKinds String(Not class: Bottom)
+            }
+        }
+
+        ^testKinds String(OK)
+    }
+    public final fun box(): R|kotlin/String| {
+        ^box R|/testData|(R|/testKinds|())
+    }
diff --git a/plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers/abstractAndSealed.kt b/plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers/abstractAndSealed.kt
new file mode 100644
index 00000000000..e3317e5579e
--- /dev/null
+++ b/plugins/kotlin-serialization/kotlin-serialization-compiler/testData/firMembers/abstractAndSealed.kt
@@ -0,0 +1,51 @@
+// WITH_STDLIB
+
+import kotlinx.serialization.*
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.json.*
+
+@Serializable
+sealed interface I
+
+@Serializable
+sealed class X: I {
+    private var x = "X"
+
+    fun exposeX() = x
+}
+
+@Serializable
+abstract class Y: X() {
+    private var y = "Y"
+
+    fun exposeY() = y
+}
+
+@Serializable
+class Bottom: Y()
+
+fun testData(results: String): String {
+    if (results != "OK") return results
+    val serial = Bottom.serializer()
+    val j = Json { encodeDefaults = true }
+    val s = j.encodeToString(serial, Bottom())
+    if (s != """{"x":"X","y":"Y"}""") return "Incorrect encoding: $s"
+    val decoded = j.decodeFromString(serial, """{"x":"1","y":"2"}""")
+    if (decoded.exposeX() != "1") return "Incorrect X"
+    if (decoded.exposeY() != "2") return "Incorrect Y"
+    return "OK"
+}
+
+@OptIn(ExperimentalSerializationApi::class)
+fun testKinds(): String {
+    if (I.serializer().descriptor.kind != PolymorphicKind.SEALED) return "Not sealed: I"
+    if (X.serializer().descriptor.kind != PolymorphicKind.SEALED) return "Not sealed: X"
+    if (Y.serializer().descriptor.kind != PolymorphicKind.OPEN) return "Not polymorphic: Y"
+    val serial = Bottom.serializer()
+    if (serial.descriptor.kind != StructureKind.CLASS) return "Not class: Bottom"
+    return "OK"
+}
+
+fun box(): String {
+    return testData(testKinds())
+}
\ No newline at end of file