diff --git a/README.md b/README.md
index 17259be..5b6fd1c 100644
--- a/README.md
+++ b/README.md
@@ -53,12 +53,15 @@ Directly from unpkg.com
 | width                  | Number          | Banner width                                                       |
 | height                 | Number          | Banner height                                                      |
 | id                     | String          | The slot ID for this banner                                        |
-| category-id            | Optional String | The category ID of the current page                                |
-| category-ids           | Optional String | Comma (,) separated list of category IDs, the item must match all  |
-| category-disjunctions  | Optional String | Comma (,) separated list of category IDs, the item must match any  |
+| category-id*           | Optional String | The category ID of the current page                                |
+| category-ids*          | Optional String | Comma (,) separated list of category IDs, the item must match all  |
+| category-disjunctions* | Optional String | Comma (,) separated list of category IDs, the item must match any  |
 | search-query           | Optional String | The search query of the current page                               |
 | location               | Optional String | The location for geotargeting                                      |
 
+\* Only one of `[category-id, category-ids, category-disjunctions]` must be set.
+If multiple are set, only the first will be considered, in that order.
+
 # Banner Behaviors
 
 | Function Name         | Arg type                                                                                        | Return Type   | Description                                                      |
diff --git a/src/index.ts b/src/index.ts
index 700d6c5..37100d7 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -208,11 +208,11 @@ export class TopsortBanner extends LitElement {
         };
       } else if (this.categoryIds) {
         auction.category = {
-          ids: this.categoryIds.split(","),
+          ids: this.categoryIds.split(",").map((item) => item.trim()),
         };
       } else if (this.categoryDisjunctions) {
         auction.category = {
-          disjunctions: this.categoryDisjunctions.split(","),
+          disjunctions: this.categoryDisjunctions.split(",").map((item) => item.trim()),
         };
       } else if (this.searchQuery) {
         auction.searchQuery = this.searchQuery;