diff --git a/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java b/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
index d97cdbaee13..90a0df7fd23 100644
--- a/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
+++ b/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
@@ -643,6 +643,10 @@ public class ExpressionCodegen extends JetVisitor {
             if (isNumberPrimitive(cls)) {
                 if (generateUnaryOp(op, asmType, expression.getBaseExpression())) return;
             }
+            else if (isClass(cls, "Boolean") && op.getName().equals("not")) {
+                generateNot(expression);
+                return;
+            }
         }
         throw new UnsupportedOperationException("Don't know how to generate this prefix expression");
     }
@@ -680,6 +684,13 @@ public class ExpressionCodegen extends JetVisitor {
         return false;
     }
 
+    private void generateNot(JetPrefixExpression expression) {
+        int oldStackSize = myStack.size();
+        gen(expression.getBaseExpression());
+        assert myStack.size() == oldStackSize+1;
+        myStack.set(myStack.size()-1, StackValue.not(myStack.get(myStack.size() - 1)));
+    }
+
     private int generateIncrement(DeclarationDescriptor op, Type asmType, JetExpression operand) {
         if (!(operand instanceof JetReferenceExpression)) {
             throw new UnsupportedOperationException("cannot increment or decrement a non-lvalue");
diff --git a/idea/src/org/jetbrains/jet/codegen/StackValue.java b/idea/src/org/jetbrains/jet/codegen/StackValue.java
index 0e7380ce1fa..fb3ae926cbb 100644
--- a/idea/src/org/jetbrains/jet/codegen/StackValue.java
+++ b/idea/src/org/jetbrains/jet/codegen/StackValue.java
@@ -36,6 +36,10 @@ public abstract class StackValue {
         return new NumberCompare(opToken);
     }
 
+    public static StackValue not(StackValue stackValue) {
+        return new Invert(stackValue);
+    }
+
     public abstract void condJump(Label label, boolean jumpIfFalse, InstructionAdapter v);
 
     private static void box(final Type type, InstructionAdapter v) {
@@ -74,6 +78,17 @@ public abstract class StackValue {
         }
     }
 
+    protected void putAsBoolean(InstructionAdapter v) {
+        Label ifTrue = new Label();
+        Label end = new Label();
+        condJump(ifTrue, false, v);
+        v.iconst(0);
+        v.goTo(end);
+        v.mark(ifTrue);
+        v.iconst(1);
+        v.mark(end);
+    }
+
     public static class Local extends StackValue {
         private final int index;
 
@@ -168,14 +183,7 @@ public abstract class StackValue {
             if (type != Type.BOOLEAN_TYPE) {
                 throw new UnsupportedOperationException("don't know how to put a compare as a non-boolean type");
             }
-            Label ifTrue = new Label();
-            Label end = new Label();
-            condJump(ifTrue, false, v);
-            v.iconst(0);
-            v.goTo(end);
-            v.mark(ifTrue);
-            v.iconst(1);
-            v.mark(end);
+            putAsBoolean(v);
         }
 
         @Override
@@ -219,4 +227,26 @@ public abstract class StackValue {
             v.visitJumpInsn(opcode, label);
         }
     }
+
+    private static class Invert extends StackValue {
+        private StackValue myOperand;
+
+        private Invert(StackValue operand) {
+            super(operand.type);
+            myOperand = operand;
+        }
+
+        @Override
+        public void put(Type type, InstructionAdapter v) {
+            if (type != Type.BOOLEAN_TYPE) {
+                throw new UnsupportedOperationException("don't know how to put a compare as a non-boolean type");
+            }
+            putAsBoolean(v);
+        }
+
+        @Override
+        public void condJump(Label label, boolean jumpIfFalse, InstructionAdapter v) {
+            myOperand.condJump(label, !jumpIfFalse, v);
+        }
+    }
 }
diff --git a/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java b/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java
index 33e69e03163..51b8c0e2002 100644
--- a/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java
+++ b/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java
@@ -437,6 +437,20 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
         assertEquals(6L, main.invoke(null, 2L));
     }
 
+    public void testBooleanNot() throws Exception {
+        loadText("fun foo(b: Boolean): Boolean = !b");
+        final Method main = generateFunction();
+        assertEquals(true, main.invoke(null, false));
+        assertEquals(false, main.invoke(null, true));
+    }
+
+    public void testBooleanNotJump() throws Exception {
+        loadText("fun foo(a: Int) : Int = if (!(a < 5)) a else 0");
+        final Method main = generateFunction();
+        assertEquals(6, main.invoke(null, 6));
+        assertEquals(0, main.invoke(null, 4));
+    }
+
     private void binOpTest(final String text, final Object arg1, final Object arg2, final Object expected) throws Exception {
         loadText(text);
         System.out.println(generateToText());