diff --git a/src/validate.janet b/src/validate.janet
index 44328e0..fdacbab 100644
--- a/src/validate.janet
+++ b/src/validate.janet
@@ -74,6 +74,10 @@ Deferred until a later iteration of Ludus:
 (defn- block [validator]
  (def ast (validator :ast))
  (def data (ast :data))
+ (when (= 0 (length data))
+  (array/push (validator :errors)
+   {:node ast :msg "blocks may not be empty"})
+  (break validator))
  (def status (validator :status))
  (set (status :toplevel) nil)
  (def tail? (status :tail))