diff --git a/bun.lockb b/bun.lockb
index 1aa0c80..6f6c34d 100755
Binary files a/bun.lockb and b/bun.lockb differ
diff --git a/package.json b/package.json
index 1b4681c..edf713a 100644
--- a/package.json
+++ b/package.json
@@ -29,10 +29,12 @@
   },
   "dependencies": {
     "hotscript": "^1.0.13",
+    "lodash-es": "^4.17.21",
     "type-fest": "^4.10.2"
   },
   "devDependencies": {
     "@rollup/plugin-node-resolve": "^15.2.3",
+    "@types/lodash-es": "^4.17.12",
     "bun-types": "latest",
     "npm-check-updates": "^16.14.14",
     "npm-sort": "^0.0.4",
diff --git a/src/TraitExpressionBuilder.ts b/src/TraitExpressionBuilder.ts
index 8ab8d30..0e9ed0d 100644
--- a/src/TraitExpressionBuilder.ts
+++ b/src/TraitExpressionBuilder.ts
@@ -1,4 +1,5 @@
 import { Call, Fn, Pipe, Tuples } from "hotscript"
+import { uniq } from "lodash-es"
 import { AbstractClass } from "type-fest"
 import { Trait } from "./Trait"
 import { TraitExpression, emptyTraitExpression } from "./TraitExpression"
@@ -96,8 +97,8 @@ class TraitExpressionBuilder<
         return new TraitExpressionBuilder(
             new TraitExpression(
                 this.expression.superclass,
-                [...this.expression.ownTraits, ...traits],
-                [...this.expression.allTraits, ...this.spreadSupertraits(traits)],
+                uniq([...this.expression.ownTraits, ...traits]) as [...OwnTraits, ...Traits],
+                uniq([...this.expression.allTraits, ...this.spreadSupertraits(traits)]) as [...AllTraits, ...SpreadSupertraits<Traits>],
             )
         )
     }