diff --git a/api/src/services/observation-service.ts b/api/src/services/observation-service.ts
index 3da3b506a4..92c1e8e260 100644
--- a/api/src/services/observation-service.ts
+++ b/api/src/services/observation-service.ts
@@ -73,7 +73,7 @@ const defaultLog = getLogger('services/observation-service');
  * enforcing uppercase object keys.
  */
 export const observationStandardColumnValidator = {
-  ITIS_TSN: { type: 'string', aliases: CSV_COLUMN_ALIASES.ITIS_TSN },
+  ITIS_TSN: { type: 'number', aliases: CSV_COLUMN_ALIASES.ITIS_TSN },
   COUNT: { type: 'number' },
   DATE: { type: 'date' },
   TIME: { type: 'string' },