diff --git a/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/checkers/FirSerializationPluginClassChecker.kt b/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/checkers/FirSerializationPluginClassChecker.kt
index d6a1d173bb2..61da06d92c2 100644
--- a/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/checkers/FirSerializationPluginClassChecker.kt
+++ b/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/checkers/FirSerializationPluginClassChecker.kt
@@ -564,14 +564,14 @@ object FirSerializationPluginClassChecker : FirClassChecker() {
         serializerType: ConeKotlinType,
         reporter: DiagnosticReporter
     ) {
-        val serializerForType = serializerType.serializerForType(session) ?: return
+        val serializerForType = serializerType.serializerForType(session)?.fullyExpandedType(session) ?: return
 
         val declarationTypeClassId = declarationType.classId
         if (declarationTypeClassId == null || declarationTypeClassId != serializerForType.classId) {
             reporter.reportOn(
                 source ?: containingClassSymbol.serializableOrMetaAnnotationSource,
                 FirSerializationErrors.SERIALIZER_TYPE_INCOMPATIBLE,
-                containingClassSymbol.defaultType(),
+                declarationType,
                 serializerType,
                 serializerForType
             )
diff --git a/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatible.fir.kt b/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatible.fir.kt
index dfb57cc907c..c98390929e9 100644
--- a/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatible.fir.kt
+++ b/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatible.fir.kt
@@ -40,3 +40,11 @@ class Foo6(@Serializable(with = NullableBazSerializer::class) val i: <!SERIALIZE
 
 @Serializable
 class Foo7(@Serializable(with = NullableBazSerializer::class) val i: <!SERIALIZER_TYPE_INCOMPATIBLE!>Bar?<!>)
+
+// It is OK to report, because subclasses can't generally be deserialized (as `deserialize()` signature returns base class)
+@Serializable
+@Suppress("FINAL_UPPER_BOUND")
+class Foo8<Br: Bar>(@Serializable(BarSerializer::class) val b: <!SERIALIZER_TYPE_INCOMPATIBLE("Br; BarSerializer; Bar")!>Br<!>)
+
+@Serializable
+class Foo9<T>(@Serializable(BarSerializer::class) val b: <!SERIALIZER_TYPE_INCOMPATIBLE("T; BarSerializer; Bar")!>T<!>)
diff --git a/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatible.kt b/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatible.kt
index 19611d0cb4a..615d05a62dc 100644
--- a/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatible.kt
+++ b/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatible.kt
@@ -40,3 +40,11 @@ class Foo6(@Serializable(with = NullableBazSerializer::class) val i: <!SERIALIZE
 
 @Serializable
 class Foo7(@Serializable(with = NullableBazSerializer::class) val i: <!SERIALIZER_TYPE_INCOMPATIBLE!>Bar?<!>)
+
+// It is OK to report, because subclasses can't generally be deserialized (as `deserialize()` signature returns base class)
+@Serializable
+@Suppress("FINAL_UPPER_BOUND")
+class Foo8<Br: Bar>(@Serializable(BarSerializer::class) val b: <!SERIALIZER_TYPE_INCOMPATIBLE("Br; BarSerializer; Bar")!>Br<!>)
+
+@Serializable
+class Foo9<T>(@Serializable(BarSerializer::class) val b: <!SERIALIZER_TYPE_INCOMPATIBLE("T; BarSerializer; Bar")!>T<!>)
diff --git a/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatibleViaTypealias.fir.kt b/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatibleViaTypealias.fir.kt
new file mode 100644
index 00000000000..71a9ac5edff
--- /dev/null
+++ b/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatibleViaTypealias.fir.kt
@@ -0,0 +1,41 @@
+// FIR_DISABLE_LAZY_RESOLVE_CHECKS
+// WITH_STDLIB
+
+// MODULE: lib
+// FILE: libtest.kt
+
+import kotlinx.serialization.*
+import java.util.*
+
+typealias MyDate = java.util.Date
+
+// MODULE: main(lib)
+// FILE: test.kt
+
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.descriptors.PrimitiveKind
+import kotlinx.serialization.descriptors.PrimitiveSerialDescriptor
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+
+internal object MyDateSerializer : KSerializer<MyDate> {
+    override val descriptor: SerialDescriptor = PrimitiveSerialDescriptor("uuid", PrimitiveKind.STRING)
+
+    override fun deserialize(decoder: Decoder) = TODO()
+
+    override fun serialize(
+        encoder: Encoder,
+        value: MyDate
+    ) = encoder.encodeString(value.toString())
+}
+
+@Serializable
+data class Session(
+    @Serializable(MyDateSerializer::class) val date: MyDate,
+    @Serializable(MyDateSerializer::class) val alsoDate: java.util.Date,
+    // The only difference with FIR is how RENDER_TYPE works:
+    @Serializable(MyDateSerializer::class) val s: <!SERIALIZER_TYPE_INCOMPATIBLE("kotlin.String; MyDateSerializer; java.util.Date")!>String<!>,
+    val sl: List<<!SERIALIZER_TYPE_INCOMPATIBLE("@Serializable(...) kotlin.String; MyDateSerializer; java.util.Date")!>@Serializable(MyDateSerializer::class) String<!>>
+)
diff --git a/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatibleViaTypealias.kt b/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatibleViaTypealias.kt
new file mode 100644
index 00000000000..81d774f89ed
--- /dev/null
+++ b/plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatibleViaTypealias.kt
@@ -0,0 +1,41 @@
+// FIR_DISABLE_LAZY_RESOLVE_CHECKS
+// WITH_STDLIB
+
+// MODULE: lib
+// FILE: libtest.kt
+
+import kotlinx.serialization.*
+import java.util.*
+
+typealias MyDate = java.util.Date
+
+// MODULE: main(lib)
+// FILE: test.kt
+
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.descriptors.PrimitiveKind
+import kotlinx.serialization.descriptors.PrimitiveSerialDescriptor
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+
+internal object MyDateSerializer : KSerializer<MyDate> {
+    override val descriptor: SerialDescriptor = PrimitiveSerialDescriptor("uuid", PrimitiveKind.STRING)
+
+    override fun deserialize(decoder: Decoder) = TODO()
+
+    override fun serialize(
+        encoder: Encoder,
+        value: MyDate
+    ) = encoder.encodeString(value.toString())
+}
+
+@Serializable
+data class Session(
+    @Serializable(MyDateSerializer::class) val date: MyDate,
+    @Serializable(MyDateSerializer::class) val alsoDate: java.util.Date,
+    // The only difference with FIR is how RENDER_TYPE works:
+    @Serializable(MyDateSerializer::class) val s: <!SERIALIZER_TYPE_INCOMPATIBLE("String; MyDateSerializer; MyDate /* = Date */")!>String<!>,
+    val sl: List<@Serializable(MyDateSerializer::class) <!SERIALIZER_TYPE_INCOMPATIBLE("String; MyDateSerializer; MyDate /* = Date */")!>String<!>>
+)
diff --git a/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirPsiDiagnosticTestGenerated.java b/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirPsiDiagnosticTestGenerated.java
index fa3c76f39ce..24dc0b4f011 100644
--- a/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirPsiDiagnosticTestGenerated.java
+++ b/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirPsiDiagnosticTestGenerated.java
@@ -164,6 +164,12 @@ public class SerializationFirPsiDiagnosticTestGenerated extends AbstractSerializ
             runTest("plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatible.kt");
         }
 
+        @Test
+        @TestMetadata("SerializerTypeIncompatibleViaTypealias.kt")
+        public void testSerializerTypeIncompatibleViaTypealias() throws Exception {
+            runTest("plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatibleViaTypealias.kt");
+        }
+
         @Test
         @TestMetadata("Transients.kt")
         public void testTransients() throws Exception {
diff --git a/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationPluginDiagnosticTestGenerated.java b/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationPluginDiagnosticTestGenerated.java
index b6f2fb9ccd4..dba8544e420 100644
--- a/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationPluginDiagnosticTestGenerated.java
+++ b/plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationPluginDiagnosticTestGenerated.java
@@ -162,6 +162,12 @@ public class SerializationPluginDiagnosticTestGenerated extends AbstractSerializ
         runTest("plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatible.kt");
     }
 
+    @Test
+    @TestMetadata("SerializerTypeIncompatibleViaTypealias.kt")
+    public void testSerializerTypeIncompatibleViaTypealias() throws Exception {
+        runTest("plugins/kotlinx-serialization/testData/diagnostics/SerializerTypeIncompatibleViaTypealias.kt");
+    }
+
     @Test
     @TestMetadata("Transients.kt")
     public void testTransients() throws Exception {