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 ff60bda04c3..e68cc3e83a0 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
@@ -24066,6 +24066,18 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
                 runTest("compiler/testData/diagnostics/tests/multiplatform/kt60902.kt");
             }
 
+            @Test
+            @TestMetadata("kt63860.kt")
+            public void testKt63860() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/multiplatform/kt63860.kt");
+            }
+
+            @Test
+            @TestMetadata("kt63860_2.kt")
+            public void testKt63860_2() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/multiplatform/kt63860_2.kt");
+            }
+
             @Test
             @TestMetadata("manyImplMemberNotImplemented.kt")
             public void testManyImplMemberNotImplemented() 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 0b812e9982c..99f3f067e19 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
@@ -24066,6 +24066,18 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
                 runTest("compiler/testData/diagnostics/tests/multiplatform/kt60902.kt");
             }
 
+            @Test
+            @TestMetadata("kt63860.kt")
+            public void testKt63860() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/multiplatform/kt63860.kt");
+            }
+
+            @Test
+            @TestMetadata("kt63860_2.kt")
+            public void testKt63860_2() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/multiplatform/kt63860_2.kt");
+            }
+
             @Test
             @TestMetadata("manyImplMemberNotImplemented.kt")
             public void testManyImplMemberNotImplemented() throws Exception {
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithLightTreeTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithLightTreeTestGenerated.java
index a31da5151b1..8fc23bd866f 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithLightTreeTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithLightTreeTestGenerated.java
@@ -313,6 +313,18 @@ public class FirOldFrontendMPPDiagnosticsWithLightTreeTestGenerated extends Abst
         runTest("compiler/testData/diagnostics/tests/multiplatform/kt60902.kt");
     }
 
+    @Test
+    @TestMetadata("kt63860.kt")
+    public void testKt63860() throws Exception {
+        runTest("compiler/testData/diagnostics/tests/multiplatform/kt63860.kt");
+    }
+
+    @Test
+    @TestMetadata("kt63860_2.kt")
+    public void testKt63860_2() throws Exception {
+        runTest("compiler/testData/diagnostics/tests/multiplatform/kt63860_2.kt");
+    }
+
     @Test
     @TestMetadata("manyImplMemberNotImplemented.kt")
     public void testManyImplMemberNotImplemented() throws Exception {
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithPsiTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithPsiTestGenerated.java
index 42aff062c05..659de132cc8 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithPsiTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithPsiTestGenerated.java
@@ -313,6 +313,18 @@ public class FirOldFrontendMPPDiagnosticsWithPsiTestGenerated extends AbstractFi
         runTest("compiler/testData/diagnostics/tests/multiplatform/kt60902.kt");
     }
 
+    @Test
+    @TestMetadata("kt63860.kt")
+    public void testKt63860() throws Exception {
+        runTest("compiler/testData/diagnostics/tests/multiplatform/kt63860.kt");
+    }
+
+    @Test
+    @TestMetadata("kt63860_2.kt")
+    public void testKt63860_2() throws Exception {
+        runTest("compiler/testData/diagnostics/tests/multiplatform/kt63860_2.kt");
+    }
+
     @Test
     @TestMetadata("manyImplMemberNotImplemented.kt")
     public void testManyImplMemberNotImplemented() throws Exception {
diff --git a/compiler/resolution.common/src/org/jetbrains/kotlin/resolve/calls/mpp/AbstractExpectActualChecker.kt b/compiler/resolution.common/src/org/jetbrains/kotlin/resolve/calls/mpp/AbstractExpectActualChecker.kt
index 0e7adabd6e6..d5cd1123a25 100644
--- a/compiler/resolution.common/src/org/jetbrains/kotlin/resolve/calls/mpp/AbstractExpectActualChecker.kt
+++ b/compiler/resolution.common/src/org/jetbrains/kotlin/resolve/calls/mpp/AbstractExpectActualChecker.kt
@@ -373,20 +373,21 @@ object AbstractExpectActualChecker {
             // "parameters" checks are required only for functions, because only functions can have parameters
             actualDeclaration is FunctionSymbolMarker && expectDeclaration is FunctionSymbolMarker
         ) {
-            val expectOverriddenDeclarations =
-                expectDeclaration.allRecursivelyOverriddenDeclarationsIncludingSelf(expectContainingClass).toSet()
-            val actualOverriddenDeclarations =
-                actualDeclaration.allRecursivelyOverriddenDeclarationsIncludingSelf(actualContainingClass).toSet()
             if (languageVersionSettings.supportsFeature(LanguageFeature.ProhibitDefaultArgumentsInExpectActualizedByFakeOverride) &&
+                // If expect declaration is a fake-override then default params came from common
+                // supertypes of actual class and expect class. It's a valid code.
+                !expectDeclaration.isFakeOverride(expectContainingClass) &&
                 (actualDeclaration.isFakeOverride(actualContainingClass) || actualDeclaration.isDelegatedMember) &&
-                // If default params came from common supertypes of actual class and expect class then it's a valid code.
-                // Here we filter out such default params.
-                (expectOverriddenDeclarations - actualOverriddenDeclarations).flatMap { it.valueParameters }
-                    .any { it.hasDefaultValueNonRecursive }
+                expectDeclaration.valueParameters.any { it.hasDefaultValueNonRecursive }
             ) {
                 return ExpectActualCheckingCompatibility.DefaultArgumentsInExpectActualizedByFakeOverride
             }
 
+            val expectOverriddenDeclarations =
+                expectDeclaration.allRecursivelyOverriddenDeclarationsIncludingSelf(expectContainingClass).toSet()
+            val actualOverriddenDeclarations =
+                actualDeclaration.allRecursivelyOverriddenDeclarationsIncludingSelf(actualContainingClass)
+
             // Actual annotation constructors can have default argument values; their consistency with arguments in the expected annotation
             // is checked in ExpectedActualDeclarationChecker.checkAnnotationConstructors
             if (!actualDeclaration.isAnnotationConstructor() &&
diff --git a/compiler/testData/diagnostics/tests/multiplatform/kt63860.kt b/compiler/testData/diagnostics/tests/multiplatform/kt63860.kt
new file mode 100644
index 00000000000..97869a300ad
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/multiplatform/kt63860.kt
@@ -0,0 +1,26 @@
+// FIR_IDENTICAL
+// MODULE: m1-common
+// FILE: common.kt
+
+expect interface SdkBufferedSink {
+    public fun write(arg: String = "default")
+}
+
+abstract class AbstractBufferedSinkAdapter() : SdkBufferedSink {
+    override fun write(arg: String) {
+    }
+}
+
+expect class BufferedSinkAdapter() : SdkBufferedSink {
+    override fun write(arg: String)
+}
+
+// MODULE: m2-jvm()()(m1-common)
+// FILE: jvm.kt
+
+actual interface SdkBufferedSink {
+    public actual fun write(arg: String): Unit
+}
+
+actual class BufferedSinkAdapter actual constructor() : AbstractBufferedSinkAdapter(), SdkBufferedSink {
+}
diff --git a/compiler/testData/diagnostics/tests/multiplatform/kt63860_2.kt b/compiler/testData/diagnostics/tests/multiplatform/kt63860_2.kt
new file mode 100644
index 00000000000..d723064224a
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/multiplatform/kt63860_2.kt
@@ -0,0 +1,26 @@
+// FIR_IDENTICAL
+// MODULE: m1-common
+// FILE: common.kt
+
+expect interface SdkBufferedSink {
+    public fun write(arg: String = "default")
+}
+
+abstract class AbstractBufferedSinkAdapter() {
+    fun write(arg: String) {
+    }
+}
+
+expect class BufferedSinkAdapter() : SdkBufferedSink {
+    override fun write(arg: String)
+}
+
+// MODULE: m2-jvm()()(m1-common)
+// FILE: jvm.kt
+
+actual interface SdkBufferedSink {
+    public actual fun write(arg: String): Unit
+}
+
+actual class BufferedSinkAdapter actual constructor() : AbstractBufferedSinkAdapter(), SdkBufferedSink {
+}
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 51ec04892dd..c52776e552a 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
@@ -24066,6 +24066,18 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/multiplatform/kt60902.kt");
             }
 
+            @Test
+            @TestMetadata("kt63860.kt")
+            public void testKt63860() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/multiplatform/kt63860.kt");
+            }
+
+            @Test
+            @TestMetadata("kt63860_2.kt")
+            public void testKt63860_2() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/multiplatform/kt63860_2.kt");
+            }
+
             @Test
             @TestMetadata("manyImplMemberNotImplemented.kt")
             public void testManyImplMemberNotImplemented() throws Exception {