diff --git a/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/InlineCodegen.kt b/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/InlineCodegen.kt
index efe2f0675d5..385a868fb98 100644
--- a/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/InlineCodegen.kt
+++ b/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/InlineCodegen.kt
@@ -577,7 +577,8 @@ abstract class InlineCodegen<out T : BaseExpressionCodegen>(
                         doCreateMethodNodeFromCompiled(directMember, state, jvmSignature.asmMethod)
                     else
                         null
-                result ?: throw IllegalStateException("Couldn't obtain compiled function body for $functionDescriptor")
+                result ?:
+                throw IllegalStateException("Couldn't obtain compiled function body for $functionDescriptor")
             }
 
             return SMAPAndMethodNode(cloneMethodNode(resultInCache.node), resultInCache.classSMAP)
diff --git a/compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java b/compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java
index e8e784a834f..2ded3076b89 100644
--- a/compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java
+++ b/compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java
@@ -14137,6 +14137,11 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/inlineClasses/mappingOfBoxedFlexibleInlineClassType.kt");
         }
 
+        @TestMetadata("multifileClass.kt")
+        public void testMultifileClass() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/multifileClass.kt");
+        }
+
         @TestMetadata("noAssertionsOnInlineClassBasedOnNullableType.kt")
         public void testNoAssertionsOnInlineClassBasedOnNullableType() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/noAssertionsOnInlineClassBasedOnNullableType.kt");
diff --git a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/irCodegenUtils.kt b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/irCodegenUtils.kt
index bda2089bc5c..6789e9a5fae 100644
--- a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/irCodegenUtils.kt
+++ b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/irCodegenUtils.kt
@@ -379,7 +379,7 @@ fun IrSimpleType.isRawType(): Boolean =
     hasAnnotation(JvmGeneratorExtensions.RAW_TYPE_ANNOTATION_FQ_NAME)
 
 internal fun classFileContainsMethod(function: IrFunction, context: JvmBackendContext, name: String): Boolean? {
-    val classId = (function.parent as? IrClass)?.classId ?: (function.containerSource as? JvmPackagePartSource)?.classId ?: return null
+    val classId = (function.containerSource as? JvmPackagePartSource)?.classId ?: (function.parent as? IrClass)?.classId ?: return null
     val originalDescriptor = context.methodSignatureMapper.mapSignatureWithGeneric(function).asmMethod.descriptor
     val descriptor = if (function.isSuspend)
         listOf(*Type.getArgumentTypes(originalDescriptor), Type.getObjectType("kotlin/coroutines/Continuation"))
diff --git a/compiler/testData/codegen/box/inlineClasses/multifileClass.kt b/compiler/testData/codegen/box/inlineClasses/multifileClass.kt
new file mode 100644
index 00000000000..64cbe4f1492
--- /dev/null
+++ b/compiler/testData/codegen/box/inlineClasses/multifileClass.kt
@@ -0,0 +1,10 @@
+// WITH_RUNTIME
+// IGNORE_BACKEND: JVM
+
+fun box(): String {
+    val uia = uintArrayOf()
+    val uia2 = uintArrayOf()
+    // UIntArray is a multifile class, so we need to know where to search for extension method copyInto.
+    uia.copyInto(uia2)
+    return "OK"
+}
diff --git a/compiler/tests-gen/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java b/compiler/tests-gen/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
index badd8b6490c..f4f9bcc5faf 100644
--- a/compiler/tests-gen/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
+++ b/compiler/tests-gen/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
@@ -15537,6 +15537,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/inlineClasses/mappingOfBoxedFlexibleInlineClassType.kt");
         }
 
+        @TestMetadata("multifileClass.kt")
+        public void testMultifileClass() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/multifileClass.kt");
+        }
+
         @TestMetadata("noAssertionsOnInlineClassBasedOnNullableType.kt")
         public void testNoAssertionsOnInlineClassBasedOnNullableType() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/noAssertionsOnInlineClassBasedOnNullableType.kt");
diff --git a/compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java b/compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
index 1dd9aaaecad..08def0da59b 100644
--- a/compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
+++ b/compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
@@ -15547,6 +15547,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/inlineClasses/mappingOfBoxedFlexibleInlineClassType.kt");
         }
 
+        @TestMetadata("multifileClass.kt")
+        public void testMultifileClass() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/multifileClass.kt");
+        }
+
         @TestMetadata("noAssertionsOnInlineClassBasedOnNullableType.kt")
         public void testNoAssertionsOnInlineClassBasedOnNullableType() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/noAssertionsOnInlineClassBasedOnNullableType.kt");
diff --git a/compiler/tests-gen/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java b/compiler/tests-gen/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
index a0604634d0d..c50562e5f82 100644
--- a/compiler/tests-gen/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
+++ b/compiler/tests-gen/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
@@ -14137,6 +14137,11 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/inlineClasses/mappingOfBoxedFlexibleInlineClassType.kt");
         }
 
+        @TestMetadata("multifileClass.kt")
+        public void testMultifileClass() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/multifileClass.kt");
+        }
+
         @TestMetadata("noAssertionsOnInlineClassBasedOnNullableType.kt")
         public void testNoAssertionsOnInlineClassBasedOnNullableType() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/noAssertionsOnInlineClassBasedOnNullableType.kt");
diff --git a/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java b/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java
index e506471fd8d..de260ede93e 100644
--- a/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java
+++ b/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java
@@ -12132,6 +12132,11 @@ public class IrJsCodegenBoxES6TestGenerated extends AbstractIrJsCodegenBoxES6Tes
             runTest("compiler/testData/codegen/box/inlineClasses/mangledSuperCalls.kt");
         }
 
+        @TestMetadata("multifileClass.kt")
+        public void testMultifileClass() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/multifileClass.kt");
+        }
+
         @TestMetadata("noAssertionsOnInlineClassBasedOnNullableType.kt")
         public void testNoAssertionsOnInlineClassBasedOnNullableType() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/noAssertionsOnInlineClassBasedOnNullableType.kt");
diff --git a/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java b/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java
index 769144f048c..479f513a644 100644
--- a/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java
+++ b/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java
@@ -12132,6 +12132,11 @@ public class IrJsCodegenBoxTestGenerated extends AbstractIrJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/inlineClasses/mangledSuperCalls.kt");
         }
 
+        @TestMetadata("multifileClass.kt")
+        public void testMultifileClass() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/multifileClass.kt");
+        }
+
         @TestMetadata("noAssertionsOnInlineClassBasedOnNullableType.kt")
         public void testNoAssertionsOnInlineClassBasedOnNullableType() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/noAssertionsOnInlineClassBasedOnNullableType.kt");
diff --git a/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java b/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java
index 1d5724cd6ad..6dbc6998acc 100644
--- a/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java
+++ b/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java
@@ -12197,6 +12197,11 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/inlineClasses/mangledSuperCalls.kt");
         }
 
+        @TestMetadata("multifileClass.kt")
+        public void testMultifileClass() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/multifileClass.kt");
+        }
+
         @TestMetadata("noAssertionsOnInlineClassBasedOnNullableType.kt")
         public void testNoAssertionsOnInlineClassBasedOnNullableType() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/noAssertionsOnInlineClassBasedOnNullableType.kt");
diff --git a/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/wasm/semantics/IrCodegenBoxWasmTestGenerated.java b/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/wasm/semantics/IrCodegenBoxWasmTestGenerated.java
index c4bbcb442e3..dfead9a57bf 100644
--- a/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/wasm/semantics/IrCodegenBoxWasmTestGenerated.java
+++ b/js/js.tests/test-gen/org/jetbrains/kotlin/js/test/wasm/semantics/IrCodegenBoxWasmTestGenerated.java
@@ -6622,6 +6622,11 @@ public class IrCodegenBoxWasmTestGenerated extends AbstractIrCodegenBoxWasmTest
             runTest("compiler/testData/codegen/box/inlineClasses/mangledSuperCalls.kt");
         }
 
+        @TestMetadata("multifileClass.kt")
+        public void testMultifileClass() throws Exception {
+            runTest("compiler/testData/codegen/box/inlineClasses/multifileClass.kt");
+        }
+
         @TestMetadata("noAssertionsOnInlineClassBasedOnNullableType.kt")
         public void testNoAssertionsOnInlineClassBasedOnNullableType() throws Exception {
             runTest("compiler/testData/codegen/box/inlineClasses/noAssertionsOnInlineClassBasedOnNullableType.kt");