diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Concat.java b/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Concat.java
index 6ed6cb5dd29..2d97b6ede04 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Concat.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Concat.java
@@ -18,7 +18,7 @@ public class Concat implements IntrinsicMethod {
         codegen.generateStringBuilderConstructor();
         if (receiver == null) {                                    // LHS.plus(RHS)
             v.swap();                                                              // StringBuilder LHS
-            codegen.invokeAppendMethod(codegen.expressionType(arguments.get(0)));  // StringBuilder(LHS)
+            codegen.invokeAppendMethod(expectedType);  // StringBuilder(LHS)
             codegen.invokeAppend(arguments.get(0));
         }
         else {                                                     // LHS + RHS
diff --git a/compiler/testData/codegen/regressions/kt446.jet b/compiler/testData/codegen/regressions/kt446.jet
new file mode 100644
index 00000000000..c148b490f81
--- /dev/null
+++ b/compiler/testData/codegen/regressions/kt446.jet
@@ -0,0 +1,5 @@
+fun box(): String {
+    var s = "s"
+    s += 1
+    return if (s == "s1") "OK" else "fail"
+}
diff --git a/compiler/tests/org/jetbrains/jet/codegen/PrimitiveTypesTest.java b/compiler/tests/org/jetbrains/jet/codegen/PrimitiveTypesTest.java
index c2365b7b71d..d667cf4598f 100644
--- a/compiler/tests/org/jetbrains/jet/codegen/PrimitiveTypesTest.java
+++ b/compiler/tests/org/jetbrains/jet/codegen/PrimitiveTypesTest.java
@@ -4,6 +4,7 @@ import java.lang.reflect.Method;
 
 /**
  * @author yole
+ * @author alex.tkachman
  */
 public class PrimitiveTypesTest extends CodegenTestCase {
     public void testPlus() throws Exception {
@@ -274,4 +275,8 @@ public class PrimitiveTypesTest extends CodegenTestCase {
     public void testKt248 () throws Exception {
         blackBoxFile("regressions/kt248.jet");
     }
+
+    public void testKt446 () throws Exception {
+        blackBoxFile("regressions/kt446.jet");
+    }
 }