diff --git a/x-pack/platform/plugins/shared/streams/server/routes/internal/streams/processing/simulation_handler.ts b/x-pack/platform/plugins/shared/streams/server/routes/internal/streams/processing/simulation_handler.ts
index cd91d50ee7616..0eae2db65996f 100644
--- a/x-pack/platform/plugins/shared/streams/server/routes/internal/streams/processing/simulation_handler.ts
+++ b/x-pack/platform/plugins/shared/streams/server/routes/internal/streams/processing/simulation_handler.ts
@@ -813,7 +813,7 @@ const computeMappingProperties = (detectedFields: NamedFieldDefinitionConfig[])
       if (config.type === 'system') {
         return [];
       }
-      return [[name, config]];
+      return [[name, { ...config, ignore_malformed: false }]];
     })
   );
 };