diff --git a/htools/Ganeti/HTools/Types.hs b/htools/Ganeti/HTools/Types.hs
index 6452f5b6d6efa2582085d875eff7ee0860443da9..ec774b012af344b0351017497e5b86fda57d97dd 100644
--- a/htools/Ganeti/HTools/Types.hs
+++ b/htools/Ganeti/HTools/Types.hs
@@ -67,6 +67,7 @@ module Ganeti.HTools.Types
     , EvacMode(..)
     ) where
 
+import Control.Monad
 import qualified Data.Map as M
 import qualified Text.JSON as JSON
 
@@ -272,6 +273,14 @@ instance Monad Result where
     return = Ok
     fail = Bad
 
+instance MonadPlus Result where
+    mzero = Bad "zero Result when used as MonadPlus"
+    -- for mplus, when we 'add' two Bad values, we concatenate their
+    -- error descriptions
+    (Bad x) `mplus` (Bad y) = Bad (x ++ "; " ++ y)
+    (Bad _) `mplus` x = x
+    x@(Ok _) `mplus` _ = x
+
 -- | Simple checker for whether a 'Result' is OK.
 isOk :: Result a -> Bool
 isOk (Ok _) = True