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 53de6a3f377..9652a21e97d 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
@@ -58,6 +58,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
             runTest("compiler/testData/diagnostics/tests/AbstractInTrait.kt");
         }
 
+        @Test
+        @TestMetadata("addTestForFalsePositiveDuplicateLabelInWhen.kt")
+        public void testAddTestForFalsePositiveDuplicateLabelInWhen() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/addTestForFalsePositiveDuplicateLabelInWhen.kt");
+        }
+
         @Test
         public void testAllFilesPresentInTests() throws Exception {
             KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/tests"), Pattern.compile("^(.+)\\.(kt|kts)$"), Pattern.compile("^(.+)\\.(reversed|fir|ll)\\.kts?$"), true);
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 4c8c5c2bf2e..e27760ec17c 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
@@ -58,6 +58,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
             runTest("compiler/testData/diagnostics/tests/AbstractInTrait.kt");
         }
 
+        @Test
+        @TestMetadata("addTestForFalsePositiveDuplicateLabelInWhen.kt")
+        public void testAddTestForFalsePositiveDuplicateLabelInWhen() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/addTestForFalsePositiveDuplicateLabelInWhen.kt");
+        }
+
         @Test
         public void testAllFilesPresentInTests() throws Exception {
             KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/tests"), Pattern.compile("^(.+)\\.(kt|kts)$"), Pattern.compile("^(.+)\\.(reversed|fir|ll)\\.kts?$"), true);
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 84a65d70a1e..5a099f9ccb6 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
@@ -58,6 +58,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
             runTest("compiler/testData/diagnostics/tests/AbstractInTrait.kt");
         }
 
+        @Test
+        @TestMetadata("addTestForFalsePositiveDuplicateLabelInWhen.kt")
+        public void testAddTestForFalsePositiveDuplicateLabelInWhen() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/addTestForFalsePositiveDuplicateLabelInWhen.kt");
+        }
+
         @Test
         public void testAllFilesPresentInTests() throws Exception {
             KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/tests"), Pattern.compile("^(.+)\\.kt$"), Pattern.compile("^(.+)\\.(reversed|fir|ll)\\.kts?$"), true, "multiplatform");
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 a00de8f5580..7ed673451e7 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
@@ -58,6 +58,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
             runTest("compiler/testData/diagnostics/tests/AbstractInTrait.kt");
         }
 
+        @Test
+        @TestMetadata("addTestForFalsePositiveDuplicateLabelInWhen.kt")
+        public void testAddTestForFalsePositiveDuplicateLabelInWhen() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/addTestForFalsePositiveDuplicateLabelInWhen.kt");
+        }
+
         @Test
         public void testAllFilesPresentInTests() throws Exception {
             KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/tests"), Pattern.compile("^(.*)\\.kts?$"), Pattern.compile("^(.+)\\.(reversed|fir|ll)\\.kts?$"), true, "multiplatform");
diff --git a/compiler/testData/diagnostics/tests/addTestForFalsePositiveDuplicateLabelInWhen.fir.kt b/compiler/testData/diagnostics/tests/addTestForFalsePositiveDuplicateLabelInWhen.fir.kt
new file mode 100644
index 00000000000..889a68decb4
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/addTestForFalsePositiveDuplicateLabelInWhen.fir.kt
@@ -0,0 +1,13 @@
+// ISSUE: KT-26045
+
+class _Class {
+    val prop_1 = 1
+}
+
+fun case_1(value: Int?, value1: _Class, value2: _Class?) {
+    when (value) {
+        value1.prop_1, value2?.prop_1 -> {}
+        10 -> {}
+    }
+}
+
diff --git a/compiler/testData/diagnostics/tests/addTestForFalsePositiveDuplicateLabelInWhen.kt b/compiler/testData/diagnostics/tests/addTestForFalsePositiveDuplicateLabelInWhen.kt
new file mode 100644
index 00000000000..76654644f6e
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/addTestForFalsePositiveDuplicateLabelInWhen.kt
@@ -0,0 +1,12 @@
+// ISSUE: KT-26045
+
+class _Class {
+    val prop_1 = 1
+}
+
+fun case_1(value: Int?, value1: _Class, value2: _Class?) {
+    when (value) {
+        value1.prop_1, <!DUPLICATE_LABEL_IN_WHEN!>value2?.prop_1<!> -> {}
+        10 -> {}
+    }
+}
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 157da9d04a9..6dc9e4e9d40 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
@@ -58,6 +58,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
             runTest("compiler/testData/diagnostics/tests/AbstractInTrait.kt");
         }
 
+        @Test
+        @TestMetadata("addTestForFalsePositiveDuplicateLabelInWhen.kt")
+        public void testAddTestForFalsePositiveDuplicateLabelInWhen() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/addTestForFalsePositiveDuplicateLabelInWhen.kt");
+        }
+
         @Test
         public void testAllFilesPresentInTests() throws Exception {
             KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/tests"), Pattern.compile("^(.*)\\.kts?$"), Pattern.compile("^(.+)\\.(reversed|fir|ll)\\.kts?$"), true);