diff --git a/.prettierrc b/.prettierrc
index 5ed59d9a65..aa4d695476 100644
--- a/.prettierrc
+++ b/.prettierrc
@@ -3,5 +3,6 @@
   "semi": false,
   "singleQuote": false,
   "tabWidth": 2,
-  "trailingComma": "es5"
-}
\ No newline at end of file
+  "trailingComma": "es5",
+  "arrowParens": "always"
+}
diff --git a/packages/medusa/src/services/line-item.js b/packages/medusa/src/services/line-item.js
index a0319d52b4..d02c582c07 100644
--- a/packages/medusa/src/services/line-item.js
+++ b/packages/medusa/src/services/line-item.js
@@ -104,7 +104,7 @@ class LineItemService extends BaseService {
       let price
       let shouldMerge = true
 
-      if (config.unit_price && typeof config.unit_price !== `undefined`) {
+      if (config.unit_price !== undefined && config.unit_price !== null) {
         // if custom unit_price, we ensure positive values
         // and we choose to not merge the items
         shouldMerge = false