diff --git a/plugins/fir-plugin-prototype/src/org/jetbrains/kotlin/ir/plugin/BodyWithDefaultValueReplacer.kt b/plugins/fir-plugin-prototype/src/org/jetbrains/kotlin/ir/plugin/BodyWithDefaultValueReplacer.kt
new file mode 100644
index 00000000000..e113619e51d
--- /dev/null
+++ b/plugins/fir-plugin-prototype/src/org/jetbrains/kotlin/ir/plugin/BodyWithDefaultValueReplacer.kt
@@ -0,0 +1,45 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.ir.plugin
+
+import org.jetbrains.kotlin.ir.IrElement
+import org.jetbrains.kotlin.ir.declarations.IrClass
+import org.jetbrains.kotlin.ir.declarations.IrFile
+import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
+import org.jetbrains.kotlin.ir.deepCopyWithVariables
+import org.jetbrains.kotlin.ir.expressions.IrReturn
+import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
+import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
+import org.jetbrains.kotlin.name.Name
+
+class BodyWithDefaultValueReplacer : IrElementVisitorVoid {
+    companion object {
+        val NAME = Name.identifier("replaceMeWithDefault")
+    }
+
+    override fun visitFile(declaration: IrFile) {
+        declaration.acceptChildrenVoid(this)
+    }
+
+    override fun visitClass(declaration: IrClass) {
+        declaration.acceptChildrenVoid(this)
+    }
+
+    override fun visitSimpleFunction(declaration: IrSimpleFunction) {
+        if (declaration.name != NAME) return
+        val defaultValue = declaration.valueParameters.first().defaultValue ?: return
+        val bodyReplacer = object : IrElementVisitorVoid {
+            override fun visitElement(element: IrElement) {
+                element.acceptChildrenVoid(this)
+            }
+
+            override fun visitReturn(expression: IrReturn) {
+                expression.value = defaultValue.expression.deepCopyWithVariables()
+            }
+        }
+        declaration.body?.acceptChildrenVoid(bodyReplacer)
+    }
+}
diff --git a/plugins/fir-plugin-prototype/src/org/jetbrains/kotlin/ir/plugin/GeneratedDeclarationsIrBodyFiller.kt b/plugins/fir-plugin-prototype/src/org/jetbrains/kotlin/ir/plugin/GeneratedDeclarationsIrBodyFiller.kt
index b7b510c0739..cfb57cdf55e 100644
--- a/plugins/fir-plugin-prototype/src/org/jetbrains/kotlin/ir/plugin/GeneratedDeclarationsIrBodyFiller.kt
+++ b/plugins/fir-plugin-prototype/src/org/jetbrains/kotlin/ir/plugin/GeneratedDeclarationsIrBodyFiller.kt
@@ -20,6 +20,7 @@ class GeneratedDeclarationsIrBodyFiller : IrGenerationExtension {
             AllPropertiesConstructorIrGenerator(pluginContext),
             TransformerForAddingAnnotations(pluginContext),
             ComposableFunctionsTransformer(pluginContext),
+            BodyWithDefaultValueReplacer(),
         )
 
         for (transformer in transformers) {
diff --git a/plugins/fir-plugin-prototype/testData/box/replaceActualFunctionBodyWitExpectDefaultValue.fir.txt b/plugins/fir-plugin-prototype/testData/box/replaceActualFunctionBodyWitExpectDefaultValue.fir.txt
new file mode 100644
index 00000000000..35cccbdac1a
--- /dev/null
+++ b/plugins/fir-plugin-prototype/testData/box/replaceActualFunctionBodyWitExpectDefaultValue.fir.txt
@@ -0,0 +1,26 @@
+Module: common
+FILE: common.kt
+    public final expect fun replaceMeWithDefault(s: R|kotlin/String| = String(OK)): R|kotlin/String|
+    public final fun commonBox(): R|kotlin/String| {
+        ^commonBox R|/replaceMeWithDefault|(String(Fail))
+    }
+FILE: main.kt
+    public final actual fun replaceMeWithDefault(s: R|kotlin/String|): R|kotlin/String| {
+        ^replaceMeWithDefault R|<local>/s|
+    }
+    public final fun box(): R|kotlin/String| {
+        ^box R|/commonBox|()
+    }
+Module: jvm
+FILE: common.kt
+    public final expect fun replaceMeWithDefault(s: R|kotlin/String| = String(OK)): R|kotlin/String|
+    public final fun commonBox(): R|kotlin/String| {
+        ^commonBox R|/replaceMeWithDefault|(String(Fail))
+    }
+FILE: main.kt
+    public final actual fun replaceMeWithDefault(s: R|kotlin/String|): R|kotlin/String| {
+        ^replaceMeWithDefault R|<local>/s|
+    }
+    public final fun box(): R|kotlin/String| {
+        ^box R|/commonBox|()
+    }
diff --git a/plugins/fir-plugin-prototype/testData/box/replaceActualFunctionBodyWitExpectDefaultValue.kt b/plugins/fir-plugin-prototype/testData/box/replaceActualFunctionBodyWitExpectDefaultValue.kt
new file mode 100644
index 00000000000..577265a1df3
--- /dev/null
+++ b/plugins/fir-plugin-prototype/testData/box/replaceActualFunctionBodyWitExpectDefaultValue.kt
@@ -0,0 +1,21 @@
+// IGNORE_BACKEND: JVM_IR
+// LANGUAGE: +MultiPlatformProjects
+// ISSUE: KT-56173
+
+// MODULE: common
+// TARGET_PLATFORM: Common
+// FILE: common.kt
+
+expect fun replaceMeWithDefault(s: String = "OK"): String
+
+fun commonBox(): String = replaceMeWithDefault("Fail")
+
+// MODULE: jvm()()(common)
+// TARGET_PLATFORM: JVM
+// FILE: main.kt
+
+actual fun replaceMeWithDefault(s: String): String = s
+
+fun box(): String {
+    return commonBox()
+}
diff --git a/plugins/fir-plugin-prototype/tests-gen/org/jetbrains/kotlin/fir/plugin/runners/FirLightTreePluginBlackBoxCodegenTestGenerated.java b/plugins/fir-plugin-prototype/tests-gen/org/jetbrains/kotlin/fir/plugin/runners/FirLightTreePluginBlackBoxCodegenTestGenerated.java
index 7c14feb9874..cd6d1dcd812 100644
--- a/plugins/fir-plugin-prototype/tests-gen/org/jetbrains/kotlin/fir/plugin/runners/FirLightTreePluginBlackBoxCodegenTestGenerated.java
+++ b/plugins/fir-plugin-prototype/tests-gen/org/jetbrains/kotlin/fir/plugin/runners/FirLightTreePluginBlackBoxCodegenTestGenerated.java
@@ -79,6 +79,12 @@ public class FirLightTreePluginBlackBoxCodegenTestGenerated extends AbstractFirL
         runTest("plugins/fir-plugin-prototype/testData/box/newSupertype.kt");
     }
 
+    @Test
+    @TestMetadata("replaceActualFunctionBodyWitExpectDefaultValue.kt")
+    public void testReplaceActualFunctionBodyWitExpectDefaultValue() throws Exception {
+        runTest("plugins/fir-plugin-prototype/testData/box/replaceActualFunctionBodyWitExpectDefaultValue.kt");
+    }
+
     @Test
     @TestMetadata("serializer.kt")
     public void testSerializer() throws Exception {