diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java
index 4e49afac2c4..a17c41fc7b2 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java
@@ -32575,6 +32575,12 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
                 runTest("compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.kt");
             }
 
+            @Test
+            @TestMetadata("whenOnClass.kt")
+            public void testWhenOnClass() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/when/whenOnClass.kt");
+            }
+
             @Test
             @TestMetadata("whenOnNothing.kt")
             public void testWhenOnNothing() throws Exception {
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java
index 7dccaf56f71..4c30206fec2 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java
@@ -32575,6 +32575,12 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 runTest("compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.kt");
             }
 
+            @Test
+            @TestMetadata("whenOnClass.kt")
+            public void testWhenOnClass() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/when/whenOnClass.kt");
+            }
+
             @Test
             @TestMetadata("whenOnNothing.kt")
             public void testWhenOnNothing() throws Exception {
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java
index 64e3f59cc50..c7aac8c8c48 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java
@@ -32575,6 +32575,12 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                 runTest("compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.kt");
             }
 
+            @Test
+            @TestMetadata("whenOnClass.kt")
+            public void testWhenOnClass() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/when/whenOnClass.kt");
+            }
+
             @Test
             @TestMetadata("whenOnNothing.kt")
             public void testWhenOnNothing() throws Exception {
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/ConeTypeCompatibilityChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/ConeTypeCompatibilityChecker.kt
index 573dbefac56..3f693ad61bb 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/ConeTypeCompatibilityChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/ConeTypeCompatibilityChecker.kt
@@ -15,6 +15,7 @@ import org.jetbrains.kotlin.fir.symbols.ConeClassLikeLookupTag
 import org.jetbrains.kotlin.fir.symbols.ConeTypeParameterLookupTag
 import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.*
+import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.StandardClassIds
 import org.jetbrains.kotlin.types.Variance
 
@@ -45,6 +46,8 @@ import org.jetbrains.kotlin.types.Variance
  */
 object ConeTypeCompatibilityChecker {
 
+    private val javaClassClassId = ClassId.fromString("java/lang/Class")
+
     /**
      * The result returned by [ConeTypeCompatibilityChecker]. Note the order of enum entries matters.
      */
@@ -146,6 +149,9 @@ object ConeTypeCompatibilityChecker {
 
         if (upperBounds.size < 2) return Compatibility.COMPATIBLE
 
+        // TODO: Due to KT-49358, we skip any checks on Java class.
+        if (upperBounds.any { it.classId == javaClassClassId }) return Compatibility.COMPATIBLE
+
         // Base types are compatible. Now we check type parameters.
 
         val typeArgumentMapping = mutableMapOf<FirTypeParameterSymbol, BoundTypeArguments>().apply {
diff --git a/compiler/testData/diagnostics/tests/when/whenOnClass.kt b/compiler/testData/diagnostics/tests/when/whenOnClass.kt
new file mode 100644
index 00000000000..bcb077a08db
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/when/whenOnClass.kt
@@ -0,0 +1,32 @@
+// FIR_IDENTICAL
+// FULL_JDK
+// WITH_RUNTIME
+// WITH_REFLECT
+
+interface A
+interface B : A
+interface C
+
+fun test1(a: A) {
+    when (a.javaClass) {
+        A::class.java -> {}
+        B::class.java -> {}
+        C::class.java -> {}
+        Any::class.java -> {}
+        else -> {}
+    }
+}
+
+class Foo : B
+class Bar
+
+fun test2(f: Foo) {
+    when (f.javaClass) {
+        Foo::class.java -> {}
+        Bar::class.java -> {}
+        A::class.java -> {}
+        B::class.java -> {}
+        C::class.java -> {}
+        Any::class.java -> {}
+    }
+}
diff --git a/compiler/testData/diagnostics/tests/when/whenOnClass.txt b/compiler/testData/diagnostics/tests/when/whenOnClass.txt
new file mode 100644
index 00000000000..961af90149a
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/when/whenOnClass.txt
@@ -0,0 +1,36 @@
+package
+
+public fun test1(/*0*/ a: A): kotlin.Unit
+public fun test2(/*0*/ f: Foo): kotlin.Unit
+
+public interface A {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface B : A {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class Bar {
+    public constructor Bar()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface C {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class Foo : B {
+    public constructor Foo()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
index e45842baca8..dbe2b35d91f 100644
--- a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
+++ b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
@@ -32671,6 +32671,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.kt");
             }
 
+            @Test
+            @TestMetadata("whenOnClass.kt")
+            public void testWhenOnClass() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/when/whenOnClass.kt");
+            }
+
             @Test
             @TestMetadata("whenOnNothing.kt")
             public void testWhenOnNothing() throws Exception {