diff --git a/src/Zenith/Core.hs b/src/Zenith/Core.hs
index 2dd74f2..45422ee 100644
--- a/src/Zenith/Core.hs
+++ b/src/Zenith/Core.hs
@@ -125,7 +125,16 @@ getCommitmentTrees ::
 getCommitmentTrees pool nodeHost nodePort znet block = do
   bh' <- getBlockHash pool block znet
   case bh' of
-    Nothing -> throwIO $ userError "couldn't get block hash"
+    Nothing -> do
+      r <-
+        makeZebraCall
+          nodeHost
+          nodePort
+          "z_gettreestate"
+          [Data.Aeson.String $ T.pack $ show block]
+      case r of
+        Left e -> throwIO $ userError e
+        Right zti -> return zti
     Just bh -> do
       r <-
         makeZebraCall