diff --git a/doerg/src/net/deertopia/doerg/tex/temml.clj b/doerg/src/net/deertopia/doerg/tex/temml.clj
index 22082fb..814635a 100644
--- a/doerg/src/net/deertopia/doerg/tex/temml.clj
+++ b/doerg/src/net/deertopia/doerg/tex/temml.clj
@@ -55,7 +55,11 @@
 (defn command-worker [x]
   (cbor/encode cbor/default-codec (:in *worker*) x)
   (.flush (:in *worker*))
-  (cbor/decode cbor/default-codec (:out *worker*)))
+  (let [r (cbor/decode cbor/default-codec (:out *worker*))]
+    (if (string? r)
+      r
+      (throw (ex-info "bad data from temml worker"
+                      {:data r})))))
 
 (defn render-inline [s]
   (command-worker s))