diff --git a/compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/codegen/FirBlackBoxCodegenTestGenerated.java b/compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/codegen/FirBlackBoxCodegenTestGenerated.java
index fdbc6ed5fd8..31d8d8f3473 100644
--- a/compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/codegen/FirBlackBoxCodegenTestGenerated.java
+++ b/compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/codegen/FirBlackBoxCodegenTestGenerated.java
@@ -5482,6 +5482,18 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/closures/kt4137.kt");
         }
 
+        @Test
+        @TestMetadata("kt47120.kt")
+        public void testKt47120() throws Exception {
+            runTest("compiler/testData/codegen/box/closures/kt47120.kt");
+        }
+
+        @Test
+        @TestMetadata("kt47120a.kt")
+        public void testKt47120a() throws Exception {
+            runTest("compiler/testData/codegen/box/closures/kt47120a.kt");
+        }
+
         @Test
         @TestMetadata("kt5589.kt")
         public void testKt5589() throws Exception {
diff --git a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/InventNamesForLocalClasses.kt b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/InventNamesForLocalClasses.kt
index 20554ada39a..56ba124106e 100644
--- a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/InventNamesForLocalClasses.kt
+++ b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/InventNamesForLocalClasses.kt
@@ -15,6 +15,7 @@ import org.jetbrains.kotlin.ir.util.isAnonymousObject
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.name.NameUtils
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.toUpperCaseAsciiOnly
 
 abstract class InventNamesForLocalClasses(private val allowTopLevelCallables: Boolean) : FileLoweringPass {
 
@@ -185,8 +186,8 @@ abstract class InventNamesForLocalClasses(private val allowTopLevelCallables: Bo
             }
 
             val simpleName = if (sourceName == null || sourceName.isSpecial) {
-                val count = (anonymousClassesCount[enclosingName] ?: 0) + 1
-                anonymousClassesCount[enclosingName] = count
+                val count = (anonymousClassesCount[enclosingName.toUpperCaseAsciiOnly()] ?: 0) + 1
+                anonymousClassesCount[enclosingName.toUpperCaseAsciiOnly()] = count
                 count.toString()
             } else {
                 sourceName
diff --git a/compiler/testData/codegen/box/closures/kt47120.kt b/compiler/testData/codegen/box/closures/kt47120.kt
new file mode 100644
index 00000000000..e34d7af6652
--- /dev/null
+++ b/compiler/testData/codegen/box/closures/kt47120.kt
@@ -0,0 +1,17 @@
+// TARGET_BACKEND: JVM
+// WITH_RUNTIME
+// FULL_JDK
+import java.util.*
+
+fun box(): String {
+    fun f() = {}
+    fun F() = {}
+
+    val class1 = f().javaClass.name
+    val class2 = F().javaClass.name
+
+    if (class1.uppercase(Locale.ENGLISH) != class2.uppercase(Locale.ENGLISH))
+        return "OK"
+    else
+        return "$class1 $class2"
+}
diff --git a/compiler/testData/codegen/box/closures/kt47120a.kt b/compiler/testData/codegen/box/closures/kt47120a.kt
new file mode 100644
index 00000000000..cd9da1ae760
--- /dev/null
+++ b/compiler/testData/codegen/box/closures/kt47120a.kt
@@ -0,0 +1,24 @@
+// TARGET_BACKEND: JVM
+// WITH_RUNTIME
+// FULL_JDK
+import java.util.*
+
+fun box(): String {
+    fun f(): Any {
+        fun g() = object {}
+        return g()
+    }
+
+    fun F(): Any {
+        fun g() = object {}
+        return g()
+    }
+
+    val class1 = f().javaClass.name
+    val class2 = F().javaClass.name
+
+    if (class1.uppercase(Locale.ENGLISH) != class2.uppercase(Locale.ENGLISH))
+        return "OK"
+    else
+        return "$class1 $class2"
+}
diff --git a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/BlackBoxCodegenTestGenerated.java b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/BlackBoxCodegenTestGenerated.java
index e22d8a3a038..27a8372953d 100644
--- a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/BlackBoxCodegenTestGenerated.java
+++ b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/BlackBoxCodegenTestGenerated.java
@@ -5482,6 +5482,18 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/closures/kt4137.kt");
         }
 
+        @Test
+        @TestMetadata("kt47120.kt")
+        public void testKt47120() throws Exception {
+            runTest("compiler/testData/codegen/box/closures/kt47120.kt");
+        }
+
+        @Test
+        @TestMetadata("kt47120a.kt")
+        public void testKt47120a() throws Exception {
+            runTest("compiler/testData/codegen/box/closures/kt47120a.kt");
+        }
+
         @Test
         @TestMetadata("kt5589.kt")
         public void testKt5589() throws Exception {
diff --git a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/IrBlackBoxCodegenTestGenerated.java b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/IrBlackBoxCodegenTestGenerated.java
index a77702910a1..0206997fcf0 100644
--- a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/IrBlackBoxCodegenTestGenerated.java
+++ b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/IrBlackBoxCodegenTestGenerated.java
@@ -5482,6 +5482,18 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/closures/kt4137.kt");
         }
 
+        @Test
+        @TestMetadata("kt47120.kt")
+        public void testKt47120() throws Exception {
+            runTest("compiler/testData/codegen/box/closures/kt47120.kt");
+        }
+
+        @Test
+        @TestMetadata("kt47120a.kt")
+        public void testKt47120a() throws Exception {
+            runTest("compiler/testData/codegen/box/closures/kt47120a.kt");
+        }
+
         @Test
         @TestMetadata("kt5589.kt")
         public void testKt5589() throws Exception {
diff --git a/compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java b/compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
index fcea44f75cb..f8bb6ba2d43 100644
--- a/compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
+++ b/compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
@@ -4778,6 +4778,16 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/closures/kt4137.kt");
         }
 
+        @TestMetadata("kt47120.kt")
+        public void testKt47120() throws Exception {
+            runTest("compiler/testData/codegen/box/closures/kt47120.kt");
+        }
+
+        @TestMetadata("kt47120a.kt")
+        public void testKt47120a() throws Exception {
+            runTest("compiler/testData/codegen/box/closures/kt47120a.kt");
+        }
+
         @TestMetadata("kt5589.kt")
         public void testKt5589() throws Exception {
             runTest("compiler/testData/codegen/box/closures/kt5589.kt");