diff --git a/src/equilibrium/render.clj b/src/equilibrium/render.clj
index 0092458..52782bd 100644
--- a/src/equilibrium/render.clj
+++ b/src/equilibrium/render.clj
@@ -176,6 +176,8 @@
                          match-str
                          (blog-sites-preview blog-name)))
         envs-fn (fn [result [match-str env-name]]
+                  (when (= nil (System/getenv env-name))
+                    (throw (ex-info (str "env var not found " env-name))))
                   (string/replace result
                                   match-str
                                   (System/getenv env-name)))]