diff --git a/idea/testData/codegen/regressions/kt259.jet b/idea/testData/codegen/regressions/kt259.jet
new file mode 100644
index 00000000000..d2ca498a3b9
--- /dev/null
+++ b/idea/testData/codegen/regressions/kt259.jet
@@ -0,0 +1,20 @@
+class A() {}
+class B<T>() {}
+
+fun box() : String {
+    val a = A()
+    System.out?.println(a is A)   //true
+    System.out?.println(a is A?)  //true
+
+    val b = B<String>()
+    System.out?.println(b is B<String>)   //true
+    System.out?.println(b is B<String>?)  //false !!!
+
+    val v = b as B<String>   //ok
+    val u = b as B<String>?  //TypeCastException
+
+    val w : B<String>? = b as B<String>   //ok
+    val x = w as B<String>?  //TypeCastException
+
+    return "OK"
+}
\ No newline at end of file
diff --git a/idea/tests/org/jetbrains/jet/codegen/TypeInfoTest.java b/idea/tests/org/jetbrains/jet/codegen/TypeInfoTest.java
index d440c3abd22..d4843618aa9 100644
--- a/idea/tests/org/jetbrains/jet/codegen/TypeInfoTest.java
+++ b/idea/tests/org/jetbrains/jet/codegen/TypeInfoTest.java
@@ -128,5 +128,10 @@ public class TypeInfoTest extends CodegenTestCase {
             }
         };
     }
+
+    public void testKt259() throws Exception {
+        blackBoxFile("regressions/kt259.jet");
+    }
+
 }
 
diff --git a/stdlib/src/jet/typeinfo/TypeInfo.java b/stdlib/src/jet/typeinfo/TypeInfo.java
index 56607c87bbf..ec93f487468 100644
--- a/stdlib/src/jet/typeinfo/TypeInfo.java
+++ b/stdlib/src/jet/typeinfo/TypeInfo.java
@@ -49,7 +49,7 @@ public class TypeInfo<T> implements JetObject {
         if (!theClass.isAssignableFrom(other.theClass)) {
             return false;
         }
-        if (nullable && !other.nullable) {
+        if (!nullable && other.nullable) {
             return false;
         }
         if (typeParameters != null) {