diff --git a/lib/coffeescript/nodes.js b/lib/coffeescript/nodes.js
index 3b9bc9b544..fc1c0d96b6 100644
--- a/lib/coffeescript/nodes.js
+++ b/lib/coffeescript/nodes.js
@@ -6987,7 +6987,11 @@
       invert() {
         var allInvertable, curr, fst, op, ref1;
         if (this.isInOperator()) {
-          this.invertOperator = '!';
+          if (this.invertOperator) {
+            this.invertOperator = void 0;
+          } else {
+            this.invertOperator = '!';
+          }
           return this;
         }
         if (this.isChain()) {
diff --git a/src/nodes.coffee b/src/nodes.coffee
index e38f85ae23..c380941720 100644
--- a/src/nodes.coffee
+++ b/src/nodes.coffee
@@ -4686,7 +4686,10 @@ exports.Op = class Op extends Base
 
   invert: ->
     if @isInOperator()
-      @invertOperator = '!'
+      if @invertOperator
+        @invertOperator = undefined
+      else
+        @invertOperator = '!'
       return @
     if @isChain()
       allInvertable = yes
diff --git a/test/operators.coffee b/test/operators.coffee
index aab8d03015..4910264c8f 100644
--- a/test/operators.coffee
+++ b/test/operators.coffee
@@ -451,3 +451,26 @@ test "'new' target", ->
 
   # classes must be called with `new`. In this case `new` applies to `get` only
   throws -> new get()()
+
+test "#5480: 'when a not in b'", ->
+  needle      = "needle"
+  hayStack    = []
+  needleStack = [needle]
+
+  switch
+    when needle     in    hayStack then ok false
+  switch
+    when needle not in    hayStack then ok true
+  switch
+    when needle     in needleStack then ok true
+  switch
+    when needle not in needleStack then ok false
+
+  switch "with subject" and true
+    when needle     in    hayStack then ok false
+  switch "with subject" and true
+    when needle not in    hayStack then ok true
+  switch "with subject" and true
+    when needle     in needleStack then ok true
+  switch "with subject" and true
+    when needle not in needleStack then ok false