diff --git a/guix-data-service/web/revision/controller.scm b/guix-data-service/web/revision/controller.scm
index 2308d01..8b6a2fe 100644
--- a/guix-data-service/web/revision/controller.scm
+++ b/guix-data-service/web/revision/controller.scm
@@ -795,8 +795,8 @@
                                  ,@(if (member "location" fields)
                                        `((location
                                           . ((file   . ,location-file)
-                                             (line   . ,location-line)
-                                             (column . ,location-column-number))))
+                                             (line   . ,(string->number location-line))
+                                             (column . ,(string->number location-column-number)))))
                                        '())
                                  ,@(if (member "licenses" fields)
                                        `((licenses