diff --git a/compiler/testData/diagnostics/tests/classObjects/deprecatedClassObjectSyntax.kt b/compiler/testData/diagnostics/tests/classObjects/deprecatedClassObjectSyntax.kt
new file mode 100644
index 00000000000..30549742c0e
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/classObjects/deprecatedClassObjectSyntax.kt
@@ -0,0 +1,28 @@
+trait G
+
+class A {
+    class object A {
+
+    }
+}
+
+trait B {
+    class object : G {
+
+    }
+}
+
+fun main() {
+    A
+    A.A
+    g(B.Default)
+    g(B)
+
+    A.ext()
+    A.A.ext()
+}
+
+fun g(g: G) { <!UNUSED_EXPRESSION!>g<!> }
+
+fun A.A.ext() {
+}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/classObjects/deprecatedClassObjectSyntax.txt b/compiler/testData/diagnostics/tests/classObjects/deprecatedClassObjectSyntax.txt
new file mode 100644
index 00000000000..11837eb49cb
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/classObjects/deprecatedClassObjectSyntax.txt
@@ -0,0 +1,38 @@
+package
+
+internal fun g(/*0*/ g: G): kotlin.Unit
+internal fun main(): kotlin.Unit
+internal fun A.A.ext(): kotlin.Unit
+
+internal final class A {
+    public constructor 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
+
+    internal default object A {
+        private constructor 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
+    }
+}
+
+internal trait B {
+    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
+
+    internal default object Default : G {
+        private constructor Default()
+        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
+    }
+}
+
+internal trait G {
+    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/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java
index 372ed030947..3429033e0a2 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java
@@ -1540,6 +1540,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("deprecatedClassObjectSyntax.kt")
+            public void testDeprecatedClassObjectSyntax() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/classObjects/deprecatedClassObjectSyntax.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("importClassInClassObject.kt")
             public void testImportClassInClassObject() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/classObjects/importClassInClassObject.kt");