diff --git a/compiler/fir/fir2ir/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java b/compiler/fir/fir2ir/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java
index ce36177dc7714..378ef87901b07 100644
--- a/compiler/fir/fir2ir/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java
+++ b/compiler/fir/fir2ir/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java
@@ -32036,6 +32036,16 @@ public void testKt25784() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/kt25784.kt");
         }
 
+        @TestMetadata("kt43286.kt")
+        public void testKt43286() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286.kt");
+        }
+
+        @TestMetadata("kt43286a.kt")
+        public void testKt43286a() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286a.kt");
+        }
+
         @TestMetadata("literalEqualsNullableUnsigned.kt")
         public void testLiteralEqualsNullableUnsigned() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/literalEqualsNullableUnsigned.kt");
diff --git a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/JvmStandardLibraryBuiltInsLowering.kt b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/JvmStandardLibraryBuiltInsLowering.kt
index 5d3a399f81e9f..73a80287ddd50 100644
--- a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/JvmStandardLibraryBuiltInsLowering.kt
+++ b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/JvmStandardLibraryBuiltInsLowering.kt
@@ -35,8 +35,8 @@ class JvmStandardLibraryBuiltInsLowering(val context: JvmBackendContext) : FileL
 
                 val parentClass = expression.symbol.owner.parent.fqNameForIrSerialization.asString()
                 val functionName = expression.symbol.owner.name.asString()
-                Jvm8builtInReplacements[parentClass to functionName]?.let {
-                    return expression.replaceWithCallTo(it)
+                jvm8builtInReplacements[parentClass to functionName]?.let { replacement ->
+                    return expression.replaceWithCallTo(replacement)
                 }
 
                 return expression
@@ -46,7 +46,7 @@ class JvmStandardLibraryBuiltInsLowering(val context: JvmBackendContext) : FileL
         irFile.transformChildren(transformer, null)
     }
 
-    private val Jvm8builtInReplacements = mapOf(
+    private val jvm8builtInReplacements = mapOf(
         ("kotlin.UInt" to "compareTo") to context.ir.symbols.compareUnsignedInt,
         ("kotlin.UInt" to "div") to context.ir.symbols.divideUnsignedInt,
         ("kotlin.UInt" to "rem") to context.ir.symbols.remainderUnsignedInt,
@@ -59,7 +59,8 @@ class JvmStandardLibraryBuiltInsLowering(val context: JvmBackendContext) : FileL
 
     // Originals are so far only instance methods, and the replacements are
     // statics, so we copy dispatch receivers to a value argument if needed.
-    private fun IrCall.replaceWithCallTo(replacement: IrSimpleFunctionSymbol) =
+    // If we can't coerce arguments to required types, keep original expression (see below).
+    private fun IrCall.replaceWithCallTo(replacement: IrSimpleFunctionSymbol): IrCall =
         IrCallImpl.fromSymbolOwner(
             startOffset,
             endOffset,
@@ -68,23 +69,30 @@ class JvmStandardLibraryBuiltInsLowering(val context: JvmBackendContext) : FileL
         ).also { newCall ->
             var valueArgumentOffset = 0
             this.dispatchReceiver?.let {
-                newCall.putValueArgument(valueArgumentOffset, it.coerceTo(replacement.owner.valueParameters[valueArgumentOffset].type))
+                val coercedDispatchReceiver = it.coerceIfPossible(replacement.owner.valueParameters[valueArgumentOffset].type)
+                    ?: return this@replaceWithCallTo
+                newCall.putValueArgument(valueArgumentOffset, coercedDispatchReceiver)
                 valueArgumentOffset++
             }
-            (0 until valueArgumentsCount).forEach {
-                newCall.putValueArgument(it + valueArgumentOffset, getValueArgument(it)!!.coerceTo(replacement.owner.valueParameters[it].type))
+            for (index in 0 until valueArgumentsCount) {
+                val coercedValueArgument = getValueArgument(index)!!.coerceIfPossible(replacement.owner.valueParameters[index].type)
+                    ?: return this@replaceWithCallTo
+                newCall.putValueArgument(index + valueArgumentOffset, coercedValueArgument)
             }
         }
 
-    private fun IrExpression.coerceTo(target: IrType): IrExpression =
-        IrCallImpl.fromSymbolOwner(
-            startOffset,
-            endOffset,
-            target,
-            context.ir.symbols.unsafeCoerceIntrinsic
-        ).also { call ->
-            call.putTypeArgument(0, type)
-            call.putTypeArgument(1, target)
-            call.putValueArgument(0, this)
-        }
+    private fun IrExpression.coerceIfPossible(toType: IrType): IrExpression? {
+        // TODO maybe UnsafeCoerce could handle types with different, but coercible underlying representations.
+        // See KT-43286 and related tests for details.
+        val fromJvmType = context.typeMapper.mapType(type)
+        val toJvmType = context.typeMapper.mapType(toType)
+        return if (fromJvmType != toJvmType)
+            null
+        else
+            IrCallImpl.fromSymbolOwner(startOffset, endOffset, toType, context.ir.symbols.unsafeCoerceIntrinsic).also { call ->
+                call.putTypeArgument(0, type)
+                call.putTypeArgument(1, toType)
+                call.putValueArgument(0, this)
+            }
+    }
 }
diff --git a/compiler/testData/codegen/box/unsignedTypes/kt43286.kt b/compiler/testData/codegen/box/unsignedTypes/kt43286.kt
new file mode 100644
index 0000000000000..ac571b4592a80
--- /dev/null
+++ b/compiler/testData/codegen/box/unsignedTypes/kt43286.kt
@@ -0,0 +1,26 @@
+// JVM_TARGET: 1.8
+// WITH_RUNTIME
+// KJS_WITH_FULL_RUNTIME
+
+class D(val x: UInt?)
+
+class E(val x: Any)
+
+fun f(d: D): String {
+    return d.x?.let { d.x.toString() } ?: ""
+}
+
+fun g(e: E): String {
+    if (e.x is UInt) return e.x.toString()
+    return ""
+}
+
+fun box(): String {
+    val test1 = f(D(42u))
+    if (test1 != "42") throw Exception(test1)
+
+    val test2 = g(E(42u))
+    if (test2 != "42") throw Exception(test2)
+
+    return "OK"
+}
\ No newline at end of file
diff --git a/compiler/testData/codegen/box/unsignedTypes/kt43286a.kt b/compiler/testData/codegen/box/unsignedTypes/kt43286a.kt
new file mode 100644
index 0000000000000..917ec50c25ecc
--- /dev/null
+++ b/compiler/testData/codegen/box/unsignedTypes/kt43286a.kt
@@ -0,0 +1,8 @@
+// JVM_TARGET: 1.8
+// WITH_RUNTIME
+// KJS_WITH_FULL_RUNTIME
+
+fun box(): String {
+    val x = 3UL % 2U
+    return if (x == 1UL) "OK" else "Fail: $x"
+}
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
index 53ecbd37c555c..442ecc7ec94dc 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
@@ -33807,6 +33807,16 @@ public void testKt25784() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/kt25784.kt");
         }
 
+        @TestMetadata("kt43286.kt")
+        public void testKt43286() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286.kt");
+        }
+
+        @TestMetadata("kt43286a.kt")
+        public void testKt43286a() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286a.kt");
+        }
+
         @TestMetadata("literalEqualsNullableUnsigned.kt")
         public void testLiteralEqualsNullableUnsigned() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/literalEqualsNullableUnsigned.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
index b0dd00e812693..beb97d7683d4b 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
@@ -31441,6 +31441,16 @@ public void testKt25784() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/kt25784.kt");
         }
 
+        @TestMetadata("kt43286.kt")
+        public void testKt43286() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286.kt");
+        }
+
+        @TestMetadata("kt43286a.kt")
+        public void testKt43286a() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286a.kt");
+        }
+
         @TestMetadata("literalEqualsNullableUnsigned.kt")
         public void testLiteralEqualsNullableUnsigned() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/literalEqualsNullableUnsigned.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
index a34cf8c824718..ed92a8e0f669e 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
@@ -32036,6 +32036,16 @@ public void testKt25784() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/kt25784.kt");
         }
 
+        @TestMetadata("kt43286.kt")
+        public void testKt43286() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286.kt");
+        }
+
+        @TestMetadata("kt43286a.kt")
+        public void testKt43286a() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286a.kt");
+        }
+
         @TestMetadata("literalEqualsNullableUnsigned.kt")
         public void testLiteralEqualsNullableUnsigned() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/literalEqualsNullableUnsigned.kt");
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java b/js/js.tests/test/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java
index fc028038110f4..ea0a206b712cb 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java
@@ -26002,6 +26002,16 @@ public void testKt25784() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/kt25784.kt");
         }
 
+        @TestMetadata("kt43286.kt")
+        public void testKt43286() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286.kt");
+        }
+
+        @TestMetadata("kt43286a.kt")
+        public void testKt43286a() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286a.kt");
+        }
+
         @TestMetadata("literalEqualsNullableUnsigned.kt")
         public void testLiteralEqualsNullableUnsigned() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/literalEqualsNullableUnsigned.kt");
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java b/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java
index 330d600d2da4e..76205ae797395 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java
@@ -26002,6 +26002,16 @@ public void testKt25784() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/kt25784.kt");
         }
 
+        @TestMetadata("kt43286.kt")
+        public void testKt43286() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286.kt");
+        }
+
+        @TestMetadata("kt43286a.kt")
+        public void testKt43286a() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286a.kt");
+        }
+
         @TestMetadata("literalEqualsNullableUnsigned.kt")
         public void testLiteralEqualsNullableUnsigned() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/literalEqualsNullableUnsigned.kt");
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java b/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java
index 1b86ccfe43b77..622042f2b5755 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java
@@ -26017,6 +26017,16 @@ public void testKt25784() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/kt25784.kt");
         }
 
+        @TestMetadata("kt43286.kt")
+        public void testKt43286() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286.kt");
+        }
+
+        @TestMetadata("kt43286a.kt")
+        public void testKt43286a() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286a.kt");
+        }
+
         @TestMetadata("literalEqualsNullableUnsigned.kt")
         public void testLiteralEqualsNullableUnsigned() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/literalEqualsNullableUnsigned.kt");
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/wasm/semantics/IrCodegenBoxWasmTestGenerated.java b/js/js.tests/test/org/jetbrains/kotlin/js/test/wasm/semantics/IrCodegenBoxWasmTestGenerated.java
index 7e513f3ed55cf..86efc618ee6fd 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/wasm/semantics/IrCodegenBoxWasmTestGenerated.java
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/wasm/semantics/IrCodegenBoxWasmTestGenerated.java
@@ -14305,6 +14305,16 @@ public void testIterateOverListOfBoxedUnsignedValues() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/iterateOverListOfBoxedUnsignedValues.kt");
         }
 
+        @TestMetadata("kt43286.kt")
+        public void testKt43286() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286.kt");
+        }
+
+        @TestMetadata("kt43286a.kt")
+        public void testKt43286a() throws Exception {
+            runTest("compiler/testData/codegen/box/unsignedTypes/kt43286a.kt");
+        }
+
         @TestMetadata("literalEqualsNullableUnsigned.kt")
         public void testLiteralEqualsNullableUnsigned() throws Exception {
             runTest("compiler/testData/codegen/box/unsignedTypes/literalEqualsNullableUnsigned.kt");