diff --git a/query_server/openapi.yaml b/query_server/openapi.yaml
index 4ab001b..b4c55a2 100644
--- a/query_server/openapi.yaml
+++ b/query_server/openapi.yaml
@@ -194,6 +194,7 @@ components:
         excludeCohortsParam:
             in: query
             name: exclude_cohorts
+            style: pipeDelimited
             description: A list of cohorts that will be excluded from results
             example: SYNTHETIC-1
             schema: