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 c7c65196c75..62af962ae72 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
@@ -5767,6 +5767,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
                     runTest("compiler/testData/diagnostics/tests/cast/neverSucceeds/CastToNotNullSuper.kt");
                 }
 
+                @Test
+                @TestMetadata("DefinitelyNotNullTypes.kt")
+                public void testDefinitelyNotNullTypes() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/cast/neverSucceeds/DefinitelyNotNullTypes.kt");
+                }
+
                 @Test
                 @TestMetadata("MappedDirect.kt")
                 public void testMappedDirect() 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 f72da269905..36153eb5a31 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
@@ -5767,6 +5767,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
                     runTest("compiler/testData/diagnostics/tests/cast/neverSucceeds/CastToNotNullSuper.kt");
                 }
 
+                @Test
+                @TestMetadata("DefinitelyNotNullTypes.kt")
+                public void testDefinitelyNotNullTypes() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/cast/neverSucceeds/DefinitelyNotNullTypes.kt");
+                }
+
                 @Test
                 @TestMetadata("MappedDirect.kt")
                 public void testMappedDirect() 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 38232a29ccf..eb0202d8de5 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
@@ -5761,6 +5761,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
                     runTest("compiler/testData/diagnostics/tests/cast/neverSucceeds/CastToNotNullSuper.kt");
                 }
 
+                @Test
+                @TestMetadata("DefinitelyNotNullTypes.kt")
+                public void testDefinitelyNotNullTypes() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/cast/neverSucceeds/DefinitelyNotNullTypes.kt");
+                }
+
                 @Test
                 @TestMetadata("MappedDirect.kt")
                 public void testMappedDirect() 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 a2b595ce56f..49764b329bf 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
@@ -5767,6 +5767,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
                     runTest("compiler/testData/diagnostics/tests/cast/neverSucceeds/CastToNotNullSuper.kt");
                 }
 
+                @Test
+                @TestMetadata("DefinitelyNotNullTypes.kt")
+                public void testDefinitelyNotNullTypes() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/cast/neverSucceeds/DefinitelyNotNullTypes.kt");
+                }
+
                 @Test
                 @TestMetadata("MappedDirect.kt")
                 public void testMappedDirect() throws Exception {
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirCastDiagnosticsHelpers.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirCastDiagnosticsHelpers.kt
index 44113bf0a4c..e992859c1fb 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirCastDiagnosticsHelpers.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirCastDiagnosticsHelpers.kt
@@ -32,8 +32,8 @@ fun checkCasting(
     isSafeCase: Boolean,
     context: CheckerContext
 ): CastingType {
-    val lhsLowerType = lhsType.lowerBoundIfFlexible()
-    val rhsLowerType = rhsType.lowerBoundIfFlexible()
+    val lhsLowerType = lhsType.lowerBoundIfFlexible().originalIfDefinitelyNotNullable()
+    val rhsLowerType = rhsType.lowerBoundIfFlexible().originalIfDefinitelyNotNullable()
 
     if (lhsLowerType is ConeErrorType || rhsLowerType is ConeErrorType) return CastingType.Possible
 
diff --git a/compiler/testData/diagnostics/tests/cast/neverSucceeds/DefinitelyNotNullTypes.kt b/compiler/testData/diagnostics/tests/cast/neverSucceeds/DefinitelyNotNullTypes.kt
new file mode 100644
index 00000000000..93c431bd36e
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/cast/neverSucceeds/DefinitelyNotNullTypes.kt
@@ -0,0 +1,6 @@
+// FIR_IDENTICAL
+
+fun <T, K> test(x: T & Any) {
+    x <!USELESS_CAST!>as (T & Any)<!>
+    x <!UNCHECKED_CAST!>as (K & Any)<!>
+}
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 a74e2befdbd..aab48e083ae 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
@@ -5767,6 +5767,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                     runTest("compiler/testData/diagnostics/tests/cast/neverSucceeds/CastToNotNullSuper.kt");
                 }
 
+                @Test
+                @TestMetadata("DefinitelyNotNullTypes.kt")
+                public void testDefinitelyNotNullTypes() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/cast/neverSucceeds/DefinitelyNotNullTypes.kt");
+                }
+
                 @Test
                 @TestMetadata("MappedDirect.kt")
                 public void testMappedDirect() throws Exception {