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 7dcd2ce69dd..f2b616f99d6 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
@@ -495,6 +495,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
       runTest("compiler/testData/diagnostics/tests/ForRangeConventions.kt");
     }
 
+    @Test
+    @TestMetadata("fpRedundantProtected.kt")
+    public void testFpRedundantProtected() {
+      runTest("compiler/testData/diagnostics/tests/fpRedundantProtected.kt");
+    }
+
     @Test
     @TestMetadata("FreeFunctionCalledAsExtension.kt")
     public void testFreeFunctionCalledAsExtension() {
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 b699f4a8342..668bb1e07e3 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
@@ -495,6 +495,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
       runTest("compiler/testData/diagnostics/tests/ForRangeConventions.kt");
     }
 
+    @Test
+    @TestMetadata("fpRedundantProtected.kt")
+    public void testFpRedundantProtected() {
+      runTest("compiler/testData/diagnostics/tests/fpRedundantProtected.kt");
+    }
+
     @Test
     @TestMetadata("FreeFunctionCalledAsExtension.kt")
     public void testFreeFunctionCalledAsExtension() {
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 da21dbf8368..709f98965e3 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
@@ -495,6 +495,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
       runTest("compiler/testData/diagnostics/tests/ForRangeConventions.kt");
     }
 
+    @Test
+    @TestMetadata("fpRedundantProtected.kt")
+    public void testFpRedundantProtected() {
+      runTest("compiler/testData/diagnostics/tests/fpRedundantProtected.kt");
+    }
+
     @Test
     @TestMetadata("FreeFunctionCalledAsExtension.kt")
     public void testFreeFunctionCalledAsExtension() {
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 70ffb17ed5a..5c59834d62c 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
@@ -495,6 +495,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
       runTest("compiler/testData/diagnostics/tests/ForRangeConventions.kt");
     }
 
+    @Test
+    @TestMetadata("fpRedundantProtected.kt")
+    public void testFpRedundantProtected() {
+      runTest("compiler/testData/diagnostics/tests/fpRedundantProtected.kt");
+    }
+
     @Test
     @TestMetadata("FreeFunctionCalledAsExtension.kt")
     public void testFreeFunctionCalledAsExtension() {
diff --git a/compiler/testData/diagnostics/tests/fpRedundantProtected.kt b/compiler/testData/diagnostics/tests/fpRedundantProtected.kt
new file mode 100644
index 00000000000..3520c14f166
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/fpRedundantProtected.kt
@@ -0,0 +1,6 @@
+// FIR_IDENTICAL
+// ISSUE: KT-66161
+
+private open class A {
+    protected fun test() {}
+}
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 85ef0cbb35f..baa16123f5f 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
@@ -495,6 +495,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
       runTest("compiler/testData/diagnostics/tests/ForRangeConventions.kt");
     }
 
+    @Test
+    @TestMetadata("fpRedundantProtected.kt")
+    public void testFpRedundantProtected() {
+      runTest("compiler/testData/diagnostics/tests/fpRedundantProtected.kt");
+    }
+
     @Test
     @TestMetadata("FreeFunctionCalledAsExtension.kt")
     public void testFreeFunctionCalledAsExtension() {