diff --git a/compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/common/OptimizationBasicInterpreter.java b/compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/common/OptimizationBasicInterpreter.java
index abec8001ec1..edf964bc907 100644
--- a/compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/common/OptimizationBasicInterpreter.java
+++ b/compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/common/OptimizationBasicInterpreter.java
@@ -50,6 +50,7 @@ public class OptimizationBasicInterpreter extends BasicInterpreter {
             case Type.SHORT:
                 return SHORT_VALUE;
             case Type.OBJECT:
+            case Type.ARRAY:
                 return new BasicValue(type);
             default:
                 return super.newValue(type);
@@ -78,13 +79,10 @@ public class OptimizationBasicInterpreter extends BasicInterpreter {
         }
 
         // if merge of two references then `lub` is java/lang/Object
-        // arrays also are BasicValues with reference type's
-        if (v.getType().getSort() == Type.OBJECT && w.getType().getSort() == Type.OBJECT) {
+        if (isReference(v) && isReference(w)) {
             return BasicValue.REFERENCE_VALUE;
         }
 
-        assert v.getType().getSort() != Type.ARRAY && w.getType().getSort() != Type.ARRAY : "There should not be arrays";
-
         // if merge of something can be stored in int var (int, char, boolean, byte, character)
         if (v.getType().getOpcode(Opcodes.ISTORE) == Opcodes.ISTORE &&
             w.getType().getOpcode(Opcodes.ISTORE) == Opcodes.ISTORE) {
@@ -93,4 +91,8 @@ public class OptimizationBasicInterpreter extends BasicInterpreter {
 
         return BasicValue.UNINITIALIZED_VALUE;
     }
+
+    private static boolean isReference(@NotNull BasicValue v) {
+        return v.getType().getSort() == Type.OBJECT || v.getType().getSort() == Type.ARRAY;
+    }
 }
diff --git a/compiler/testData/codegen/box/coroutines/kt12958.kt b/compiler/testData/codegen/box/coroutines/kt12958.kt
new file mode 100644
index 00000000000..978b80c54a5
--- /dev/null
+++ b/compiler/testData/codegen/box/coroutines/kt12958.kt
@@ -0,0 +1,36 @@
+class Controller {
+    var result = "fail"
+    suspend fun <V> suspendHere(v: V, x: Continuation<V>) {
+        x.resume(v)
+    }
+
+    operator fun handleResult(x: String, c: Continuation<Nothing>) {
+        result = x
+    }
+}
+
+fun builder(coroutine c: Controller.() -> Continuation<Unit>): String {
+    val controller = Controller()
+    c(controller).resume(Unit)
+
+    return controller.result
+}
+
+fun foo(): String = builder {
+    // A piece of code for next statement:
+    // INVOKEVIRTUAL suspendHere
+    // CHECKCAST [B
+    //
+    // Analyzer uses `newValue` method for estimation of type generated by CHECKCAST insn,
+    // but for arrays `newValue` returned just Basic.REFERENCE_VALUE, thus we didn't add necessary checkcasts
+    // for variables spilled into fields
+    val data2 = suspendHere(ByteArray(2))
+
+    suspendHere("<ignored>")
+    data2.size.toString()
+}
+
+fun box(): String {
+    if (foo() != "2") return "fail 1"
+    return "OK"
+}
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
index 443eab96765..ecb2629a266 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
@@ -4201,6 +4201,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
 
+        @TestMetadata("kt12958.kt")
+        public void testKt12958() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/coroutines/kt12958.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("lambdaParameters.kt")
         public void testLambdaParameters() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/coroutines/lambdaParameters.kt");