diff --git a/compiler/testData/codegen/box/inlineClasses/kt28879.kt b/compiler/testData/codegen/box/inlineClasses/kt28879.kt
new file mode 100644
index 00000000000..3b6fda847de
--- /dev/null
+++ b/compiler/testData/codegen/box/inlineClasses/kt28879.kt
@@ -0,0 +1,19 @@
+// WITH_REFLECT
+// TARGET_BACKEND: JVM
+// IGNORE_BACKEND: JVM_IR
+
+import java.util.concurrent.atomic.AtomicReference
+import java.util.Arrays
+
+fun box(): String {
+    val a0 = AtomicReference(0.toUByte()).get().javaClass
+    val a1 = AtomicReference(0u).get().javaClass
+
+    val b = Arrays.asList(42u).first().javaClass
+
+    if (a0.toString() != "class kotlin.UByte") return "Fail 1"
+    if (a1.toString() != "class kotlin.UInt") return "Fail 2"
+    if (b.toString() != "class kotlin.UInt") return "Fail 3"
+
+    return "OK"
+}
\ No newline at end of file
diff --git a/compiler/testData/codegen/box/inlineClasses/mappingOfBoxedFlexibleInlineClassType.kt b/compiler/testData/codegen/box/inlineClasses/mappingOfBoxedFlexibleInlineClassType.kt
new file mode 100644
index 00000000000..92828881fc5
--- /dev/null
+++ b/compiler/testData/codegen/box/inlineClasses/mappingOfBoxedFlexibleInlineClassType.kt
@@ -0,0 +1,35 @@
+// WITH_RUNTIME
+// TARGET_BACKEND: JVM
+// IGNORE_BACKEND: JVM_IR
+
+// FILE: JavaClass.java
+
+public class JavaClass {
+    public static <T> T id(T x) { return x; }
+}
+
+// FILE: test.kt
+
+inline class IcInt(val i: Int)
+inline class IcLong(val l: Long)
+inline class IcAny(val a: Any?)
+inline class IcOverIc(val o: IcInt)
+
+fun box(): String {
+    val i = IcInt(1)
+    val l = IcLong(2)
+    val a = IcAny("string")
+    val o = IcOverIc(IcInt(3))
+
+    val ij = JavaClass.id(i)
+    val lj = JavaClass.id(l)
+    val aj = JavaClass.id(a)
+    val oj = JavaClass.id(o)
+
+    if (ij.i != 1) return "Fail 1"
+    if (lj.l != 2L) return "Fail 2"
+    if (aj.a != "string") return "Fail 3"
+    if (oj.o.i != 3) return "Fail 4"
+
+    return "OK"
+}
\ No newline at end of file
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
index 6998669dfef..9b1552bf0c6 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
@@ -12145,11 +12145,21 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/inlineClasses/kt28585.kt");
         }
 
+        @TestMetadata("kt28879.kt")
+        public void testKt28879() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/kt28879.kt");
+        }
+
         @TestMetadata("mapInlineClassesWithSuppressWildcardsMode.kt")
         public void testMapInlineClassesWithSuppressWildcardsMode() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/mapInlineClassesWithSuppressWildcardsMode.kt");
         }
 
+        @TestMetadata("mappingOfBoxedFlexibleInlineClassType.kt")
+        public void testMappingOfBoxedFlexibleInlineClassType() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/mappingOfBoxedFlexibleInlineClassType.kt");
+        }
+
         @TestMetadata("noAssertionsOnInlineClassBasedOnNullableType.kt")
         public void testNoAssertionsOnInlineClassBasedOnNullableType() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/noAssertionsOnInlineClassBasedOnNullableType.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
index 476c9f814dc..3f44395327c 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
@@ -12145,11 +12145,21 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/inlineClasses/kt28585.kt");
         }
 
+        @TestMetadata("kt28879.kt")
+        public void testKt28879() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/kt28879.kt");
+        }
+
         @TestMetadata("mapInlineClassesWithSuppressWildcardsMode.kt")
         public void testMapInlineClassesWithSuppressWildcardsMode() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/mapInlineClassesWithSuppressWildcardsMode.kt");
         }
 
+        @TestMetadata("mappingOfBoxedFlexibleInlineClassType.kt")
+        public void testMappingOfBoxedFlexibleInlineClassType() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/mappingOfBoxedFlexibleInlineClassType.kt");
+        }
+
         @TestMetadata("noAssertionsOnInlineClassBasedOnNullableType.kt")
         public void testNoAssertionsOnInlineClassBasedOnNullableType() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/noAssertionsOnInlineClassBasedOnNullableType.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
index e131642a1e4..0120c831a4d 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
@@ -12150,11 +12150,21 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/inlineClasses/kt28585.kt");
         }
 
+        @TestMetadata("kt28879.kt")
+        public void testKt28879() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/kt28879.kt");
+        }
+
         @TestMetadata("mapInlineClassesWithSuppressWildcardsMode.kt")
         public void testMapInlineClassesWithSuppressWildcardsMode() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/mapInlineClassesWithSuppressWildcardsMode.kt");
         }
 
+        @TestMetadata("mappingOfBoxedFlexibleInlineClassType.kt")
+        public void testMappingOfBoxedFlexibleInlineClassType() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/mappingOfBoxedFlexibleInlineClassType.kt");
+        }
+
         @TestMetadata("noAssertionsOnInlineClassBasedOnNullableType.kt")
         public void testNoAssertionsOnInlineClassBasedOnNullableType() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/noAssertionsOnInlineClassBasedOnNullableType.kt");
diff --git a/core/descriptors.jvm/src/org/jetbrains/kotlin/load/kotlin/typeSignatureMapping.kt b/core/descriptors.jvm/src/org/jetbrains/kotlin/load/kotlin/typeSignatureMapping.kt
index 5672c22e015..70897a74798 100644
--- a/core/descriptors.jvm/src/org/jetbrains/kotlin/load/kotlin/typeSignatureMapping.kt
+++ b/core/descriptors.jvm/src/org/jetbrains/kotlin/load/kotlin/typeSignatureMapping.kt
@@ -284,7 +284,7 @@ internal fun computeExpandedTypeInner(kotlinType: KotlinType, visitedClassifiers
             val underlyingType = kotlinType.substitutedUnderlyingType() ?: return null
             val expandedUnderlyingType = computeExpandedTypeInner(underlyingType, visitedClassifiers) ?: return null
             when {
-                !kotlinType.isMarkedNullable -> expandedUnderlyingType
+                !kotlinType.isNullable() -> expandedUnderlyingType
 
                 // Here inline class type is nullable. Apply nullability to the expandedUnderlyingType.