diff --git a/2018-edition/ferris.css b/2018-edition/ferris.css
index ed9b77df2..84ba401af 100644
--- a/2018-edition/ferris.css
+++ b/2018-edition/ferris.css
@@ -1,16 +1,21 @@
 body.light .does_not_compile,
 body.light .panics,
+body.light .not_desired_behavior,
 body.rust .does_not_compile,
-body.rust .panics {
+body.rust .panics,
+body.rust .not_desired_behavior {
   background: #fff1f1;
 }
 
 body.coal .does_not_compile,
 body.coal .panics,
+body.coal .not_desired_behavior,
 body.navy .does_not_compile,
 body.navy .panics,
+body.navy .not_desired_behavior,
 body.ayu .does_not_compile,
-body.ayu .panics {
+body.ayu .panics,
+body.ayu .not_desired_behavior {
   background: #501f21;
 }
 
diff --git a/2018-edition/ferris.js b/2018-edition/ferris.js
index f5fb54503..9d37861cf 100644
--- a/2018-edition/ferris.js
+++ b/2018-edition/ferris.js
@@ -2,6 +2,7 @@ var ferrisTypes = [
   'does_not_compile',
   'panics',
   'unsafe',
+  'not_desired_behavior',
 ]
 
 document.addEventListener('DOMContentLoaded', () => {
diff --git a/2018-edition/src/img/ferris/not_desired_behavior.svg b/2018-edition/src/img/ferris/not_desired_behavior.svg
new file mode 100644
index 000000000..47f402455
--- /dev/null
+++ b/2018-edition/src/img/ferris/not_desired_behavior.svg
@@ -0,0 +1,75 @@
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