diff --git a/native/commonizer/src/org/jetbrains/kotlin/commonizer/cir/utils.kt b/native/commonizer/src/org/jetbrains/kotlin/commonizer/cir/utils.kt
index 38b01137ea7..1bdb573482f 100644
--- a/native/commonizer/src/org/jetbrains/kotlin/commonizer/cir/utils.kt
+++ b/native/commonizer/src/org/jetbrains/kotlin/commonizer/cir/utils.kt
@@ -85,27 +85,25 @@ internal tailrec fun computeExpandedType(underlyingType: CirClassOrTypeAliasType
 internal inline fun CirDeclaration.unsupported(): Nothing = error("This method should never be called on ${this::class.java}, $this")
 
 internal fun CirClassOrTypeAliasType.withParentArguments(
-    parentArguments: List<CirTypeProjection>, parentIsMarkedNullable: Boolean
+    parentArguments: List<CirTypeProjection>
 ): CirClassOrTypeAliasType {
-    val newIsMarkedNullable = isMarkedNullable || parentIsMarkedNullable
-
     val newArguments = arguments.map { oldArgument ->
         if (oldArgument !is CirRegularTypeProjection) return@map oldArgument
 
         when (val type = oldArgument.type) {
             is CirTypeParameterType -> parentArguments[type.index]
             is CirClassOrTypeAliasType -> CirRegularTypeProjection(
-                oldArgument.projectionKind, type.withParentArguments(parentArguments, parentIsMarkedNullable)
+                oldArgument.projectionKind, type.withParentArguments(parentArguments)
             )
             else -> oldArgument
         }
     }
 
-    return when (val newType = makeNullableIfNecessary(newIsMarkedNullable).withArguments(newArguments)) {
+    return when (val newType = withArguments(newArguments)) {
         this -> this
         is CirClassType -> newType
         is CirTypeAliasType -> newType.withUnderlyingType(
-            newType.underlyingType.withParentArguments(parentArguments, newIsMarkedNullable)
+            newType.underlyingType.withParentArguments(parentArguments)
         )
     }
 }
diff --git a/native/commonizer/src/org/jetbrains/kotlin/commonizer/core/ClassOrTypeAliasTypeCommonizer.kt b/native/commonizer/src/org/jetbrains/kotlin/commonizer/core/ClassOrTypeAliasTypeCommonizer.kt
index ca2661aa859..52b2b7aa088 100644
--- a/native/commonizer/src/org/jetbrains/kotlin/commonizer/core/ClassOrTypeAliasTypeCommonizer.kt
+++ b/native/commonizer/src/org/jetbrains/kotlin/commonizer/core/ClassOrTypeAliasTypeCommonizer.kt
@@ -90,7 +90,8 @@ internal class ClassOrTypeAliasTypeCommonizer(
                 arguments = arguments,
                 isMarkedNullable = isMarkedNullable,
                 underlyingType = dependencyClassifier.underlyingType.toCirClassOrTypeAliasTypeOrNull(classifiers.commonDependencies)
-                    ?.withParentArguments(arguments, isMarkedNullable) ?: return null
+                    ?.makeNullableIfNecessary(isMarkedNullable)
+                    ?.withParentArguments(arguments) ?: return null
             )
 
             else -> Unit
@@ -114,7 +115,9 @@ internal class ClassOrTypeAliasTypeCommonizer(
                 typeAliasId = classifierId,
                 arguments = arguments,
                 isMarkedNullable = isMarkedNullable,
-                underlyingType = commonizedClassifier.underlyingType.withParentArguments(arguments, isMarkedNullable)
+                underlyingType = commonizedClassifier.underlyingType
+                    .makeNullableIfNecessary(isMarkedNullable)
+                    .withParentArguments(arguments)
             )
 
             else -> null
diff --git a/native/commonizer/tests/org/jetbrains/kotlin/commonizer/hierarchical/ParameterizedTypesCommonizationTest.kt b/native/commonizer/tests/org/jetbrains/kotlin/commonizer/hierarchical/ParameterizedTypesCommonizationTest.kt
index e0a231286bb..f4d67d6c0f4 100644
--- a/native/commonizer/tests/org/jetbrains/kotlin/commonizer/hierarchical/ParameterizedTypesCommonizationTest.kt
+++ b/native/commonizer/tests/org/jetbrains/kotlin/commonizer/hierarchical/ParameterizedTypesCommonizationTest.kt
@@ -582,7 +582,7 @@ class ParameterizedTypesCommonizationTest : AbstractInlineSourcesCommonizationTe
         )
     }
 
-    fun `test KT-51686`() {
+    fun `test KT-51686 - type argument is parameterized class`() {
         val result = commonize {
             outputTarget("(a, b)")
             "a" withSource """
@@ -618,4 +618,99 @@ class ParameterizedTypesCommonizationTest : AbstractInlineSourcesCommonizationTe
             """.trimIndent()
         )
     }
+
+    fun `test KT-51686 - type argument is parameterized class - nullability - 0`() {
+        val result = commonize {
+            outputTarget("(a, b)")
+            "a" withSource """
+                class A
+                class Y<T>
+                class X<T>
+                typealias TA<T> = X<Y<T>>
+                fun f(): TA<A>? = null!!
+            """.trimIndent()
+
+            "b" withSource """
+                class A
+                class Y<T>
+                class X<T>
+                typealias TA<T> = X<Y<T>>
+                fun f(): TA<A>? = null!!
+            """.trimIndent()
+        }
+
+        result.assertCommonized(
+            "(a, b)", """
+                expect class A()
+                expect class Y<T>()
+                expect class X<T>()
+                typealias TA<T> = X<Y<T>>
+                expect fun f(): TA<A>?
+            """.trimIndent()
+        )
+    }
+
+    fun `test KT-51686 - type argument is parameterized class - nullability - 1`() {
+        val result = commonize {
+            outputTarget("(a, b)")
+            "a" withSource """
+                class A<T>
+                class X<T>
+                typealias TA1<T> = X<T>
+                typealias TA2<T> = X<T>?
+                                
+                val p1: A<TA1<Unit>> get() = null!!
+                val p2: A<TA1<Unit?> get() = null!!
+                val p3: A<TA1<Unit>?> get() = null!!
+                val p4: A<TA2<Unit>> get() = null!!
+                val p5: A<TA2<Unit?>> get() = null!!
+                val p6: A<TA2<Unit>?> get() = null!!
+                val p7: A<TA1<Unit>>? get() = null!!
+                val p8: TA2<A<Unit>> get() = null!!
+                val p9: TA2<A<Unit>?> get() = null!!
+                val p10: TA2<Unit> get() = null!!
+                fun<T> f1(): A<TA1<TA2<T>>> = null!! 
+            """.trimIndent()
+
+            "b" withSource """
+                class A<T>
+                class X<T>
+                typealias TA1<T> = X<T>
+                typealias TA2<T> = X<T>?
+                                
+                val p1: A<TA1<Unit>> get() = null!!
+                val p2: A<TA1<Unit?> get() = null!!
+                val p3: A<TA1<Unit>?> get() = null!!
+                val p4: A<TA2<Unit>> get() = null!!
+                val p5: A<TA2<Unit?>> get() = null!!
+                val p6: A<TA2<Unit>?> get() = null!!
+                val p7: A<TA1<Unit>>? get() = null!!
+                val p8: TA2<A<Unit>> get() = null!!
+                val p9: TA2<A<Unit>?> get() = null!!
+                val p10: TA2<Unit> get() = null!!
+                fun<T> f1(): A<TA1<TA2<T>>> = null!! 
+            """.trimIndent()
+        }
+
+        result.assertCommonized(
+            "(a, b)", """
+                expect class A<T>()
+                expect class X<T>()
+                typealias TA1<T> = X<T>
+                typealias TA2<T> = X<T>?
+                
+                expect val p1: A<TA1<Unit>> 
+                expect val p2: A<TA1<Unit?> 
+                expect val p3: A<TA1<Unit>?>
+                expect val p4: A<TA2<Unit>?>
+                expect val p5: A<TA2<Unit?>?>
+                expect val p6: A<TA2<Unit>?>
+                expect val p7: A<TA1<Unit>>?
+                expect val p8: TA2<A<Unit>>?
+                expect val p9: TA2<A<Unit>?>?
+                expect val p10: TA2<Unit>?
+                expect fun<T> f1(): A<TA1<TA2<T>?>>
+            """.trimIndent()
+        )
+    }
 }