diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java
index de5ec49228b..e708eb2a7ae 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java
@@ -23693,6 +23693,18 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
                     runTest("compiler/testData/diagnostics/tests/modifiers/const/kCallable_before.kt");
                 }
 
+                @Test
+                @TestMetadata("kClassInEquals.kt")
+                public void testKClassInEquals() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/modifiers/const/kClassInEquals.kt");
+                }
+
+                @Test
+                @TestMetadata("kClassInStringConcatenation.kt")
+                public void testKClassInStringConcatenation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/modifiers/const/kClassInStringConcatenation.kt");
+                }
+
                 @Test
                 @TestMetadata("kotlinJavaCycle.kt")
                 public void testKotlinJavaCycle() throws Exception {
diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java
index ec6af487215..0628dd5fb59 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java
@@ -23693,6 +23693,18 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
                     runTest("compiler/testData/diagnostics/tests/modifiers/const/kCallable_before.kt");
                 }
 
+                @Test
+                @TestMetadata("kClassInEquals.kt")
+                public void testKClassInEquals() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/modifiers/const/kClassInEquals.kt");
+                }
+
+                @Test
+                @TestMetadata("kClassInStringConcatenation.kt")
+                public void testKClassInStringConcatenation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/modifiers/const/kClassInStringConcatenation.kt");
+                }
+
                 @Test
                 @TestMetadata("kotlinJavaCycle.kt")
                 public void testKotlinJavaCycle() throws Exception {
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java
index 4ab6adbb7b0..97e4a82998a 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java
@@ -23687,6 +23687,18 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
                     runTest("compiler/testData/diagnostics/tests/modifiers/const/kCallable_before.kt");
                 }
 
+                @Test
+                @TestMetadata("kClassInEquals.kt")
+                public void testKClassInEquals() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/modifiers/const/kClassInEquals.kt");
+                }
+
+                @Test
+                @TestMetadata("kClassInStringConcatenation.kt")
+                public void testKClassInStringConcatenation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/modifiers/const/kClassInStringConcatenation.kt");
+                }
+
                 @Test
                 @TestMetadata("kotlinJavaCycle.kt")
                 public void testKotlinJavaCycle() throws Exception {
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java
index 944a73fd1c6..4c89450709c 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java
@@ -23693,6 +23693,18 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
                     runTest("compiler/testData/diagnostics/tests/modifiers/const/kCallable_before.kt");
                 }
 
+                @Test
+                @TestMetadata("kClassInEquals.kt")
+                public void testKClassInEquals() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/modifiers/const/kClassInEquals.kt");
+                }
+
+                @Test
+                @TestMetadata("kClassInStringConcatenation.kt")
+                public void testKClassInStringConcatenation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/modifiers/const/kClassInStringConcatenation.kt");
+                }
+
                 @Test
                 @TestMetadata("kotlinJavaCycle.kt")
                 public void testKotlinJavaCycle() throws Exception {
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirConstChecks.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirConstChecks.kt
index 6ff4982e27a..b6cd2b8a541 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirConstChecks.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirConstChecks.kt
@@ -85,7 +85,7 @@ internal fun checkConstantArguments(
         }
         expression is FirStringConcatenationCall -> {
             for (exp in (expression as FirCall).arguments) {
-                if (exp is FirResolvedQualifier || expression.isForbiddenComplexConstant(session)) {
+                if (exp is FirResolvedQualifier || exp is FirGetClassCall) {
                     return ConstantArgumentKind.NOT_CONST
                 }
                 checkConstantArguments(exp, session)?.let { return it }
@@ -95,8 +95,13 @@ internal fun checkConstantArguments(
             if (expression.operation == FirOperation.IDENTITY || expression.operation == FirOperation.NOT_IDENTITY) {
                 return ConstantArgumentKind.NOT_CONST
             }
+
+            if (expression.isForbiddenComplexConstant(session)) {
+                return ConstantArgumentKind.NOT_CONST
+            }
+
             for (exp in (expression as FirCall).arguments) {
-                if (exp is FirResolvedQualifier || expression.isForbiddenComplexConstant(session) || exp.getExpandedType().isUnsignedType) {
+                if (exp is FirResolvedQualifier || exp is FirGetClassCall || exp.getExpandedType().isUnsignedType) {
                     return ConstantArgumentKind.NOT_CONST
                 }
                 checkConstantArguments(exp, session)?.let { return it }
diff --git a/compiler/testData/diagnostics/tests/modifiers/const/kClassInEquals.kt b/compiler/testData/diagnostics/tests/modifiers/const/kClassInEquals.kt
new file mode 100644
index 00000000000..77a94a10c80
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/modifiers/const/kClassInEquals.kt
@@ -0,0 +1,10 @@
+// FIR_IDENTICAL
+annotation class Anno(val equal: Boolean)
+
+class A
+class B
+
+@Anno(<!ANNOTATION_ARGUMENT_MUST_BE_CONST!>A::class == B::class<!>)
+class C
+
+const val equal = <!CONST_VAL_WITH_NON_CONST_INITIALIZER!>A::class == B::class<!>
diff --git a/compiler/testData/diagnostics/tests/modifiers/const/kClassInStringConcatenation.kt b/compiler/testData/diagnostics/tests/modifiers/const/kClassInStringConcatenation.kt
new file mode 100644
index 00000000000..6e6cd0c8fd5
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/modifiers/const/kClassInStringConcatenation.kt
@@ -0,0 +1,11 @@
+// FIR_IDENTICAL
+annotation class Anno(val str: String)
+
+@Anno(<!ANNOTATION_ARGUMENT_MUST_BE_CONST!>"${A::class}"<!>)
+class A
+
+@Anno(<!ANNOTATION_ARGUMENT_MUST_BE_CONST!>B::class.toString()<!>)
+class B
+
+const val a = <!CONST_VAL_WITH_NON_CONST_INITIALIZER!>"${A::class}"<!>
+const val b = <!CONST_VAL_WITH_NON_CONST_INITIALIZER!>B::class.toString()<!>
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 e228afe9fa5..4b077cb6f26 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
@@ -23693,6 +23693,18 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                     runTest("compiler/testData/diagnostics/tests/modifiers/const/kCallable_before.kt");
                 }
 
+                @Test
+                @TestMetadata("kClassInEquals.kt")
+                public void testKClassInEquals() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/modifiers/const/kClassInEquals.kt");
+                }
+
+                @Test
+                @TestMetadata("kClassInStringConcatenation.kt")
+                public void testKClassInStringConcatenation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/modifiers/const/kClassInStringConcatenation.kt");
+                }
+
                 @Test
                 @TestMetadata("kotlinJavaCycle.kt")
                 public void testKotlinJavaCycle() throws Exception {