diff --git a/compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject.kt b/compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject.kt
new file mode 100644
index 00000000000..314af0fb29b
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject.kt
@@ -0,0 +1,39 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE!
+// ISSUE: KT-28999
+
+fun case_1() {
+    val x = object<T> { } // type of x is <anonymous object><T>
+}
+
+fun case_2() {
+    val x = object<T : Number, K: Comparable<K>> { }
+}
+
+fun case_3() {
+    val x = object<T> <!SYNTAX!>where <!DEBUG_INFO_MISSING_UNRESOLVED!>T<!> : <!DEBUG_INFO_MISSING_UNRESOLVED!>Comparable<!><<!DEBUG_INFO_MISSING_UNRESOLVED!>T<!>><!> { } // ERROR: Where clause is not allowed for objects
+}
+
+val x = object<T, K: Comparable<K>> {
+    fun test() = 10 <!UNCHECKED_CAST!>as T<!> // OK
+}
+
+fun case_4() {
+    val x = object<T> {
+        fun test() = 10 <!UNCHECKED_CAST!>as T<!>
+    }
+
+    val y = x.test() // type y is T
+}
+
+inline fun <reified T> case_5() {
+    val x = object<T> {
+        fun test() = 10 <!UNCHECKED_CAST!>as T<!>
+    }
+
+    val z = x.test()
+
+    if (z is T) {
+        // z is {T!! & T!!} (smart cast from T)
+        <!UNRESOLVED_REFERENCE!>println<!>(z)
+    }
+}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject.txt b/compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject.txt
new file mode 100644
index 00000000000..b67d9a855e1
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject.txt
@@ -0,0 +1,8 @@
+package
+
+public val x: kotlin.Any
+public fun case_1(): kotlin.Unit
+public fun case_2(): kotlin.Unit
+public fun case_3(): kotlin.Unit
+public fun case_4(): kotlin.Unit
+public inline fun </*0*/ reified T> case_5(): kotlin.Unit
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
index 7a72b9457d9..b4b5e5f88e6 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
@@ -3109,6 +3109,11 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 runTest("compiler/testData/diagnostics/tests/classObjects/resolveFunctionInsideClassObject.kt");
             }
 
+            @TestMetadata("typeParametersInAnnonymousObject.kt")
+            public void testTypeParametersInAnnonymousObject() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject.kt");
+            }
+
             @TestMetadata("typeParametersInObject.kt")
             public void testTypeParametersInObject() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/classObjects/typeParametersInObject.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java
index 6c2f2459178..406f3af861f 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java
@@ -3104,6 +3104,11 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                 runTest("compiler/testData/diagnostics/tests/classObjects/resolveFunctionInsideClassObject.kt");
             }
 
+            @TestMetadata("typeParametersInAnnonymousObject.kt")
+            public void testTypeParametersInAnnonymousObject() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/classObjects/typeParametersInAnnonymousObject.kt");
+            }
+
             @TestMetadata("typeParametersInObject.kt")
             public void testTypeParametersInObject() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/classObjects/typeParametersInObject.kt");