diff --git a/lib/lexer.js b/lib/lexer.js
index 14ab39af..191a587d 100644
--- a/lib/lexer.js
+++ b/lib/lexer.js
@@ -141,7 +141,7 @@
         tag = 'LEADING_WHEN';
       }
       this.i += id.length;
-      if (!accessed) {
+      if (!(accessed)) {
         if (include(COFFEE_ALIASES, id)) {
           tag = (id = CONVERSIONS[id]);
         }
diff --git a/lib/nodes.js b/lib/nodes.js
index c8a24a6c..69cfd5f4 100644
--- a/lib/nodes.js
+++ b/lib/nodes.js
@@ -845,7 +845,7 @@
           props.push(prop);
         }
       }
-      if (!constructor) {
+      if (!(constructor)) {
         if (this.parent) {
           applied = new ValueNode(this.parent, [new AccessorNode(literal('apply'))]);
           constructor = new AssignNode(this.variable, new CodeNode([], new Expressions([new CallNode(applied, [literal('this'), literal('arguments')])])));
@@ -1202,7 +1202,7 @@
       o.top = true;
       cond = this.condition.compile(o);
       set = '';
-      if (!top) {
+      if (!(top)) {
         rvar = o.scope.free_variable();
         set = ("" + this.tab + rvar + " = [];\n");
         if (this.body) {
@@ -1535,7 +1535,7 @@
         } else if (name) {
           var_part = ("" + body_dent + name + " = " + svar + "[" + ivar + "];\n");
         }
-        if (!this.object) {
+        if (!(this.object)) {
           lvar = scope.free_variable();
           step_part = this.step ? ("" + ivar + " += " + (this.step.compile(o))) : ("" + ivar + "++");
           for_part = ("" + ivar + " = 0, " + lvar + " = " + (svar) + ".length; " + ivar + " < " + lvar + "; " + step_part);
diff --git a/src/lexer.coffee b/src/lexer.coffee
index 6de5f202..538e238e 100644
--- a/src/lexer.coffee
+++ b/src/lexer.coffee
@@ -96,7 +96,7 @@ exports.Lexer: class Lexer
     @identifier_error id      if include RESERVED, id
     tag: 'LEADING_WHEN'       if tag is 'WHEN' and include LINE_BREAK, @tag()
     @i: + id.length
-    if not accessed
+    unless accessed
       tag: id: CONVERSIONS[id]         if include COFFEE_ALIASES, id
       return @tag_half_assignment tag  if @prev() and @prev()[0] is 'ASSIGN' and include HALF_ASSIGNMENTS, tag
     @token tag, id
diff --git a/src/nodes.coffee b/src/nodes.coffee
index 9340d958..45e39b8f 100644
--- a/src/nodes.coffee
+++ b/src/nodes.coffee
@@ -612,7 +612,7 @@ exports.ClassNode: class ClassNode extends BaseNode
           prop:   new AssignNode(val, func)
         props.push prop
 
-    if not constructor
+    unless constructor
       if @parent
         applied: new ValueNode(@parent, [new AccessorNode(literal('apply'))])
         constructor: new AssignNode(@variable, new CodeNode([], new Expressions([
@@ -878,7 +878,7 @@ exports.WhileNode: class WhileNode extends BaseNode
     o.top:      true
     cond:       @condition.compile(o)
     set:        ''
-    if not top
+    unless top
       rvar:     o.scope.free_variable()
       set:      "$@tab$rvar = [];\n"
       @body:    PushNode.wrap(rvar, @body) if @body
@@ -1129,7 +1129,7 @@ exports.ForNode: class ForNode extends BaseNode
         var_part:   new AssignNode(@name, literal("$svar[$ivar]")).compile(merge o, {indent: @idt(1), top: true}) + "\n"
       else
         var_part:   "$body_dent$name = $svar[$ivar];\n" if name
-      if not @object
+      unless @object
         lvar:       scope.free_variable()
         step_part:  if @step then "$ivar += ${ @step.compile(o) }" else "$ivar++"
         for_part:   "$ivar = 0, $lvar = ${svar}.length; $ivar < $lvar; $step_part"
@@ -1188,7 +1188,7 @@ exports.IfNode: class IfNode extends BaseNode
   # Ensure that the switch expression isn't evaluated more than once.
   rewrite_switch: (o) ->
     assigner: @switcher
-    if not (@switcher.unwrap() instanceof LiteralNode)
+    unless @switcher.unwrap() instanceof LiteralNode
       variable: literal(o.scope.free_variable())
       assigner: new AssignNode(variable, @switcher)
       @switcher: variable