diff --git a/lib/nodes.js b/lib/nodes.js
index a41acd6f..7aa45dda 100644
--- a/lib/nodes.js
+++ b/lib/nodes.js
@@ -1322,6 +1322,7 @@
     return While;
   }();
   exports.Op = Op = function() {
+    var CONVERSIONS, INVERSIONS;
     function Op(op, first, second, flip) {
       if (op === 'in') {
         return new In(first, second);
@@ -1334,18 +1335,18 @@
           first = new Parens(first);
         }
       }
-      this.operator = this.CONVERSIONS[op] || op;
+      this.operator = CONVERSIONS[op] || op;
       this.first = first;
       this.second = second;
       this.flip = !!flip;
     }
     __extends(Op, Base);
-    Op.prototype.CONVERSIONS = {
+    CONVERSIONS = {
       '==': '===',
       '!=': '!==',
       'of': 'in'
     };
-    Op.prototype.INVERSIONS = {
+    INVERSIONS = {
       '!==': '===',
       '===': '!==',
       '>': '<=',
@@ -1362,12 +1363,14 @@
       return (_ref = this.operator) === '<' || _ref === '>' || _ref === '>=' || _ref === '<=' || _ref === '===' || _ref === '!==';
     };
     Op.prototype.invert = function() {
-      var op;
-      if (op = this.INVERSIONS[this.operator]) {
+      var fst, op, _ref;
+      if (op = INVERSIONS[this.operator]) {
         this.operator = op;
         return this;
       } else if (this.second) {
         return new Parens(this).invert();
+      } else if (this.operator === '!' && (fst = this.first.unwrap()) instanceof Op && ((_ref = fst.operator) === '!' || _ref === 'in' || _ref === 'instanceof')) {
+        return fst;
       } else {
         return new Op('!', this);
       }
diff --git a/src/nodes.coffee b/src/nodes.coffee
index 31d2c6fc..0e31105f 100644
--- a/src/nodes.coffee
+++ b/src/nodes.coffee
@@ -1047,19 +1047,19 @@ exports.Op = class Op extends Base
     if op is 'new'
       return first.newInstance() if first instanceof Call
       first = new Parens first   if first instanceof Code and first.bound
-    @operator = @CONVERSIONS[op] or op
+    @operator = CONVERSIONS[op] or op
     @first    = first
     @second   = second
     @flip     = !!flip
 
   # The map of conversions from CoffeeScript to JavaScript symbols.
-  CONVERSIONS:
+  CONVERSIONS =
     '==': '==='
     '!=': '!=='
     'of': 'in'
 
   # The map of invertible operators.
-  INVERSIONS:
+  INVERSIONS =
     '!==': '==='
     '===': '!=='
     '>':   '<='
@@ -1078,11 +1078,14 @@ exports.Op = class Op extends Base
     @operator in ['<', '>', '>=', '<=', '===', '!==']
 
   invert: ->
-    if op = @INVERSIONS[@operator]
+    if op = INVERSIONS[@operator]
       @operator = op
       this
     else if @second
       new Parens(this).invert()
+    else if @operator is '!' and (fst = @first.unwrap()) instanceof Op and
+                                  fst.operator in ['!', 'in', 'instanceof']
+      fst
     else
       new Op '!', this
 
diff --git a/test/test_switch.coffee b/test/test_switch.coffee
index 79616e20..bf48580b 100644
--- a/test/test_switch.coffee
+++ b/test/test_switch.coffee
@@ -54,11 +54,17 @@ ok result
 
 # Should be able to handle switches sans-condition.
 result = switch
-  when null then 1
-  when 'truthful string' then 2
-  else 3
+  when null                     then 0
+  when !1                       then 1
+  when '' not of {''}           then 2
+  when [] not instanceof Array  then 3
+  when true is false            then 4
+  when 'x' < 'y' > 'z'          then 5
+  when 'a' in ['b', 'c']        then 6
+  when 'd' in (['e', 'f'])      then 7
+  else ok
 
-ok result is 2
+eq result, ok
 
 
 # Should be able to use "@properties" within the switch clause.