diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt
index 0eb9184d020..1c91ab3482b 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt
@@ -229,7 +229,14 @@ private fun FirCallableSymbol<*>.toSymbolForCall(
         }
         // Member fake override or bound callable reference
         dispatchReceiver !is FirNoReceiverExpression -> {
-            dispatchReceiver.typeRef.coneType.let { it.findClassRepresentation(it, declarationStorage.session) }
+            val callSiteDispatchReceiverType = dispatchReceiver.typeRef.coneType
+            val declarationSiteDispatchReceiverType = dispatchReceiverType
+            val type = if (callSiteDispatchReceiverType is ConeDynamicType && declarationSiteDispatchReceiverType != null) {
+                declarationSiteDispatchReceiverType
+            } else {
+                callSiteDispatchReceiverType
+            }
+            type.findClassRepresentation(type, declarationStorage.session)
         }
         // Unbound callable reference to member (non-extension)
         isReference && fir.receiverParameter == null -> {
@@ -752,4 +759,4 @@ fun FirCallableDeclaration.contextReceiversForFunctionOrContainingProperty(): Li
 
 fun IrActualizationResult?.extractFirDeclarations(): Set<FirDeclaration>? {
     return this?.actualizedExpectDeclarations?.mapNotNullTo(mutableSetOf()) { ((it as IrMetadataSourceOwner).metadata as FirMetadataSource).fir }
-}
\ No newline at end of file
+}
diff --git a/compiler/testData/codegen/box/smartCasts/smartcastOnDynamic.kt b/compiler/testData/codegen/box/smartCasts/smartcastOnDynamic.kt
new file mode 100644
index 00000000000..20f9d815559
--- /dev/null
+++ b/compiler/testData/codegen/box/smartCasts/smartcastOnDynamic.kt
@@ -0,0 +1,13 @@
+// TARGET_BACKEND: JS_IR
+// ISSUE: KT-57682
+fun test_1(x: String) = x.length
+
+fun test_2(x: dynamic): Int = when (x) {
+    is String -> x.length
+    else -> x.something
+}
+
+fun box(): String {
+    val result = test_1("a") + test_2("ab")
+    return if (result == 3) "OK" else "fail"
+}
diff --git a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/fir/FirJsCodegenBoxTestGenerated.java b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/fir/FirJsCodegenBoxTestGenerated.java
index 7523c434fa7..736e6f3a499 100644
--- a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/fir/FirJsCodegenBoxTestGenerated.java
+++ b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/fir/FirJsCodegenBoxTestGenerated.java
@@ -35055,6 +35055,12 @@ public class FirJsCodegenBoxTestGenerated extends AbstractFirJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/smartCasts/smartCastInsideIf.kt");
         }
 
+        @Test
+        @TestMetadata("smartcastOnDynamic.kt")
+        public void testSmartcastOnDynamic() throws Exception {
+            runTest("compiler/testData/codegen/box/smartCasts/smartcastOnDynamic.kt");
+        }
+
         @Test
         @TestMetadata("whenSmartCast.kt")
         public void testWhenSmartCast() throws Exception {
diff --git a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrJsCodegenBoxTestGenerated.java b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrJsCodegenBoxTestGenerated.java
index 7900ea46ea1..2eaa51c2186 100644
--- a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrJsCodegenBoxTestGenerated.java
+++ b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrJsCodegenBoxTestGenerated.java
@@ -35055,6 +35055,12 @@ public class IrJsCodegenBoxTestGenerated extends AbstractIrJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/smartCasts/smartCastInsideIf.kt");
         }
 
+        @Test
+        @TestMetadata("smartcastOnDynamic.kt")
+        public void testSmartcastOnDynamic() throws Exception {
+            runTest("compiler/testData/codegen/box/smartCasts/smartcastOnDynamic.kt");
+        }
+
         @Test
         @TestMetadata("whenSmartCast.kt")
         public void testWhenSmartCast() throws Exception {
diff --git a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrJsES6CodegenBoxTestGenerated.java b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrJsES6CodegenBoxTestGenerated.java
index 7762c2a8dbc..2efe308ced9 100644
--- a/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrJsES6CodegenBoxTestGenerated.java
+++ b/js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/IrJsES6CodegenBoxTestGenerated.java
@@ -35055,6 +35055,12 @@ public class IrJsES6CodegenBoxTestGenerated extends AbstractIrJsES6CodegenBoxTes
             runTest("compiler/testData/codegen/box/smartCasts/smartCastInsideIf.kt");
         }
 
+        @Test
+        @TestMetadata("smartcastOnDynamic.kt")
+        public void testSmartcastOnDynamic() throws Exception {
+            runTest("compiler/testData/codegen/box/smartCasts/smartcastOnDynamic.kt");
+        }
+
         @Test
         @TestMetadata("whenSmartCast.kt")
         public void testWhenSmartCast() throws Exception {