diff --git a/src/org/jetbrains/jet/j2k/Converter.kt b/src/org/jetbrains/jet/j2k/Converter.kt
index 88b2f6e82e5..22aa988310a 100644
--- a/src/org/jetbrains/jet/j2k/Converter.kt
+++ b/src/org/jetbrains/jet/j2k/Converter.kt
@@ -414,15 +414,14 @@ public open class Converter() {
         var expression: Expression = expressionToExpression(argument)
         val actualType: PsiType? = argument.getType()
         val isPrimitiveTypeOrNull: Boolean = actualType == null || actualType is PsiPrimitiveType
-        var isRef: Boolean = ((argument is PsiReferenceExpression && argument.isQualified()) || argument is PsiMethodCallExpression)
-        if (isPrimitiveTypeOrNull && isRef && expression.isNullable()) {
+        if (isPrimitiveTypeOrNull && expression.isNullable()) {
             expression = BangBangExpression(expression)
         }
 
         if (actualType != null) {
             if (isConversionNeeded(actualType, expectedType) && !(expression is LiteralExpression))
             {
-                var conversion: String? = PRIMITIVE_TYPE_CONVERSIONS?.get(expectedType?.getCanonicalText())
+                var conversion: String? = PRIMITIVE_TYPE_CONVERSIONS.get(expectedType?.getCanonicalText())
                 if (conversion != null)
                 {
                     expression = DummyMethodCallExpression(expression, conversion, (Identifier.EMPTY_IDENTIFIER as IdentifierImpl?))
diff --git a/src/org/jetbrains/jet/j2k/ast/IfStatement.java b/src/org/jetbrains/jet/j2k/ast/IfStatement.java
deleted file mode 100644
index 1efa8311a56..00000000000
--- a/src/org/jetbrains/jet/j2k/ast/IfStatement.java
+++ /dev/null
@@ -1,48 +0,0 @@
-/*
- * Copyright 2010-2012 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.jetbrains.jet.j2k.ast;
-
-import org.jetbrains.annotations.NotNull;
-
-/**
- * @author ignatov
- */
-public class IfStatement extends Expression {
-    private final Expression myCondition;
-    private final Statement myThenStatement;
-    private final Statement myElseStatement;
-
-    public IfStatement(Expression condition, Statement thenStatement, Statement elseStatement) {
-        myCondition = condition;
-        myThenStatement = thenStatement;
-        myElseStatement = elseStatement;
-    }
-
-    @NotNull
-    @Override
-    public String toKotlin() {
-        String result = "if" + SPACE + "(" + myCondition.toKotlin() + ")" + N + myThenStatement.toKotlin() + N;
-
-        if (myElseStatement != Statement.EMPTY_STATEMENT) {
-            return result +
-                   "else" + N +
-                   myElseStatement.toKotlin();
-        }
-
-        return result;
-    }
-}
diff --git a/src/org/jetbrains/jet/j2k/ast/IfStatement.kt b/src/org/jetbrains/jet/j2k/ast/IfStatement.kt
new file mode 100644
index 00000000000..65915e24c49
--- /dev/null
+++ b/src/org/jetbrains/jet/j2k/ast/IfStatement.kt
@@ -0,0 +1,13 @@
+package org.jetbrains.jet.j2k.ast
+
+
+public open class IfStatement(val condition: Expression, val thenStatement: Statement, val elseStatement: Statement): Expression() {
+    public override fun toKotlin(): String {
+        val result: String = "if (" + condition.toKotlin() + ")\n" + thenStatement.toKotlin() + "\n"
+        if (elseStatement != Statement.EMPTY_STATEMENT) {
+            return result + "else\n" + elseStatement.toKotlin()
+        }
+
+        return result
+    }
+}
diff --git a/src/org/jetbrains/jet/j2k/ast/PostfixOperator.java b/src/org/jetbrains/jet/j2k/ast/PostfixOperator.java
deleted file mode 100644
index 3b6eafdefac..00000000000
--- a/src/org/jetbrains/jet/j2k/ast/PostfixOperator.java
+++ /dev/null
@@ -1,38 +0,0 @@
-/*
- * Copyright 2010-2012 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.jetbrains.jet.j2k.ast;
-
-import org.jetbrains.annotations.NotNull;
-
-/**
- * @author ignatov
- */
-public class PostfixOperator extends Expression {
-    private final String myOp;
-    private final Expression myExpression;
-
-    public PostfixOperator(String op, Expression expression) {
-        myOp = op;
-        myExpression = expression;
-    }
-
-    @NotNull
-    @Override
-    public String toKotlin() {
-        return myExpression.toKotlin() + myOp;
-    }
-}
diff --git a/src/org/jetbrains/jet/j2k/ast/PostfixOperator.kt b/src/org/jetbrains/jet/j2k/ast/PostfixOperator.kt
new file mode 100644
index 00000000000..3f71a035c13
--- /dev/null
+++ b/src/org/jetbrains/jet/j2k/ast/PostfixOperator.kt
@@ -0,0 +1,6 @@
+package org.jetbrains.jet.j2k.ast
+
+
+public open class PostfixOperator(val op: String, val expression: Expression): Expression() {
+    public override fun toKotlin() = expression.toKotlin() + op
+}
diff --git a/src/org/jetbrains/jet/j2k/ast/PrefixOperator.java b/src/org/jetbrains/jet/j2k/ast/PrefixOperator.java
deleted file mode 100644
index 28b4c92cff9..00000000000
--- a/src/org/jetbrains/jet/j2k/ast/PrefixOperator.java
+++ /dev/null
@@ -1,38 +0,0 @@
-/*
- * Copyright 2010-2012 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.jetbrains.jet.j2k.ast;
-
-import org.jetbrains.annotations.NotNull;
-
-/**
- * @author ignatov
- */
-public class PrefixOperator extends Expression {
-    private final String myOp;
-    private final Expression myExpression;
-
-    public PrefixOperator(String op, Expression expression) {
-        myOp = op;
-        myExpression = expression;
-    }
-
-    @NotNull
-    @Override
-    public String toKotlin() {
-        return myOp + myExpression.toKotlin();
-    }
-}
diff --git a/src/org/jetbrains/jet/j2k/ast/PrefixOperator.kt b/src/org/jetbrains/jet/j2k/ast/PrefixOperator.kt
new file mode 100644
index 00000000000..d8db37ea52b
--- /dev/null
+++ b/src/org/jetbrains/jet/j2k/ast/PrefixOperator.kt
@@ -0,0 +1,7 @@
+package org.jetbrains.jet.j2k.ast
+
+
+public open class PrefixOperator(val op: String, val expression: Expression): Expression() {
+    public override fun toKotlin() = op + expression.toKotlin()
+    public override fun isNullable() = expression.isNullable()
+}
diff --git a/src/org/jetbrains/jet/j2k/visitors/StatementVisitor.java b/src/org/jetbrains/jet/j2k/visitors/StatementVisitor.java
index a5988afc5ac..32aeef3a88b 100644
--- a/src/org/jetbrains/jet/j2k/visitors/StatementVisitor.java
+++ b/src/org/jetbrains/jet/j2k/visitors/StatementVisitor.java
@@ -205,9 +205,7 @@ public class StatementVisitor extends ElementVisitor {
         super.visitIfStatement(statement);
         PsiExpression condition = statement.getCondition();
         @SuppressWarnings("ConstantConditions")
-        Expression expression = condition != null && condition.getType() != null ?
-                this.getConverter().expressionToExpression(condition, condition.getType()) :
-                                getConverter().expressionToExpression(condition);
+        Expression expression = getConverter().expressionToExpression(condition, PsiType.BOOLEAN);
         myResult = new IfStatement(
                 expression,
                 getConverter().statementToStatement(statement.getThenBranch()),
diff --git a/tests/testData/ast/issues/file/kt-824-isDir.kt b/tests/testData/ast/issues/file/kt-824-isDir.kt
index 1879496fd0b..34e7ddca7ec 100644
--- a/tests/testData/ast/issues/file/kt-824-isDir.kt
+++ b/tests/testData/ast/issues/file/kt-824-isDir.kt
@@ -3,7 +3,7 @@ import java.io.File
 public open class Test() {
 class object {
 public open fun isDir(parent : File?) : Boolean {
-if (parent == null || !parent?.exists())
+if (parent == null || !parent?.exists()!!)
 {
 return false
 }
diff --git a/tests/testData/ast/prefixOperator/statement/nullableIf.jav b/tests/testData/ast/prefixOperator/statement/nullableIf.jav
new file mode 100644
index 00000000000..539180d48fb
--- /dev/null
+++ b/tests/testData/ast/prefixOperator/statement/nullableIf.jav
@@ -0,0 +1,2 @@
+String s = null;
+if (!s.isEmpty()) { }
diff --git a/tests/testData/ast/prefixOperator/statement/nullableIf.kt b/tests/testData/ast/prefixOperator/statement/nullableIf.kt
new file mode 100644
index 00000000000..bd253b95ddf
--- /dev/null
+++ b/tests/testData/ast/prefixOperator/statement/nullableIf.kt
@@ -0,0 +1,4 @@
+var s : String? = null
+if (!s?.isEmpty()!!)
+{
+}
\ No newline at end of file