diff --git a/packages/entity/src/behavior-components/expression.jsx b/packages/entity/src/behavior-components/expression.jsx
index 6d3f7ba..cb531b1 100644
--- a/packages/entity/src/behavior-components/expression.jsx
+++ b/packages/entity/src/behavior-components/expression.jsx
@@ -274,6 +274,7 @@ const Expression = ({
       className={classnames(
         'expression',
         {'wrong-type': realType !== type},
+        {'undefined-type': 'undefined' === realType},
       )}
     >
       {Renderables}
diff --git a/packages/entity/src/behavior-components/expression.scss b/packages/entity/src/behavior-components/expression.scss
index e44f7a8..34f04e5 100644
--- a/packages/entity/src/behavior-components/expression.scss
+++ b/packages/entity/src/behavior-components/expression.scss
@@ -7,7 +7,11 @@
     color: #00bdd6;
   }
   &.wrong-type {
-    background-color: rgba(255, 0, 0, 0.4);
+    background-color: rgb(180, 0, 0);
+    padding: 0.5em;
+  }
+  &.undefined-type {
+    background-color: rgb(180, 180, 0);
     padding: 0.5em;
   }
   > .expression {