diff --git a/hnix-store-remote/src/System/Nix/Store/Remote/Arbitrary.hs b/hnix-store-remote/src/System/Nix/Store/Remote/Arbitrary.hs
index 56e39b1..a487fa1 100644
--- a/hnix-store-remote/src/System/Nix/Store/Remote/Arbitrary.hs
+++ b/hnix-store-remote/src/System/Nix/Store/Remote/Arbitrary.hs
@@ -78,9 +78,6 @@ deriving via GenericArbitrary GCAction
 deriving via GenericArbitrary GCOptions
   instance Arbitrary GCOptions
 
-deriving via GenericArbitrary GCResult
-  instance Arbitrary GCResult
-
 -- * Handshake
 
 deriving via GenericArbitrary WorkerMagic
@@ -94,6 +91,8 @@ deriving via GenericArbitrary TrustedFlag
 deriving via GenericArbitrary WorkerOp
   instance Arbitrary WorkerOp
 
+-- ** Request
+
 instance Arbitrary (Some StoreRequest) where
   arbitrary = oneof
     [ Some <$> (AddToStore <$> arbitrary <*> arbitrary <*> arbitrary <*> pure RepairMode_DontRepair)
@@ -121,3 +120,11 @@ instance Arbitrary (Some StoreRequest) where
     , pure $ Some SyncWithGC
     , Some <$> (VerifyStore <$> arbitrary <*> arbitrary)
     ]
+
+-- ** Reply
+
+deriving via GenericArbitrary GCResult
+  instance Arbitrary GCResult
+
+deriving via GenericArbitrary Missing
+  instance Arbitrary Missing
diff --git a/hnix-store-remote/src/System/Nix/Store/Remote/Serializer.hs b/hnix-store-remote/src/System/Nix/Store/Remote/Serializer.hs
index c5fd1b3..39ca8ac 100644
--- a/hnix-store-remote/src/System/Nix/Store/Remote/Serializer.hs
+++ b/hnix-store-remote/src/System/Nix/Store/Remote/Serializer.hs
@@ -92,6 +92,8 @@ module System.Nix.Store.Remote.Serializer
   , buildResult
   -- *** GCResult
   , gcResult
+  -- *** Missing
+  , missing
   ) where
 
 import Control.Monad.Except (MonadError, throwError, )
@@ -1341,6 +1343,7 @@ data ReplySError
   | ReplySError_PrimPut SError
   | ReplySError_DerivationOutput SError
   | ReplySError_GCResult SError
+  | ReplySError_Missing SError
   | ReplySError_Realisation SError
   | ReplySError_RealisationWithId SError
   deriving (Eq, Ord, Generic, Show)
@@ -1453,3 +1456,23 @@ gcResult = mapErrorS ReplySError_GCResult $ Serializer
       putS int gcResultBytesFreed
       putS (int @Word64) 0 -- obsolete
   }
+
+missing
+  :: HasStoreDir r
+  => NixSerializer r ReplySError Missing
+missing = mapErrorS ReplySError_Missing $ Serializer
+  { getS = do
+      missingWillBuild <- getS (hashSet storePath)
+      missingWillSubstitute <- getS (hashSet storePath)
+      missingUnknownPaths <- getS (hashSet storePath)
+      missingDownloadSize <- getS int
+      missingNarSize <- getS int
+
+      pure Missing{..}
+  , putS = \Missing{..} -> do
+      putS (hashSet storePath) missingWillBuild
+      putS (hashSet storePath) missingWillSubstitute
+      putS (hashSet storePath) missingUnknownPaths
+      putS int missingDownloadSize
+      putS int missingNarSize
+  }
diff --git a/hnix-store-remote/src/System/Nix/Store/Remote/Types/StoreReply.hs b/hnix-store-remote/src/System/Nix/Store/Remote/Types/StoreReply.hs
index 94fa2c0..185147d 100644
--- a/hnix-store-remote/src/System/Nix/Store/Remote/Types/StoreReply.hs
+++ b/hnix-store-remote/src/System/Nix/Store/Remote/Types/StoreReply.hs
@@ -6,6 +6,7 @@ import System.Nix.Build (BuildResult)
 import System.Nix.StorePath (HasStoreDir(..), StorePath)
 import System.Nix.Store.Remote.Serializer
 import System.Nix.Store.Remote.Types.GC (GCResult)
+import System.Nix.Store.Remote.Types.Query.Missing (Missing)
 import System.Nix.Store.Remote.Types.ProtoVersion (HasProtoVersion)
 
 -- | Get @NixSerializer@ for some type @a@
@@ -29,6 +30,9 @@ instance StoreReply BuildResult where
 instance StoreReply GCResult where
   getReplyS = gcResult
 
+instance StoreReply Missing where
+  getReplyS = missing
+
 instance StoreReply StorePath where
   getReplyS = mapPrimE storePath
 
diff --git a/hnix-store-remote/tests/NixSerializerSpec.hs b/hnix-store-remote/tests/NixSerializerSpec.hs
index e50a1f0..d2ba74d 100644
--- a/hnix-store-remote/tests/NixSerializerSpec.hs
+++ b/hnix-store-remote/tests/NixSerializerSpec.hs
@@ -151,6 +151,7 @@ spec = parallel $ do
 
   describe "StoreReply" $ do
     prop "GCResult" $ roundtripSReader @StoreDir gcResult
+    prop "Missing" $ roundtripSReader @StoreDir missing
 
 restrictProtoVersion :: ProtoVersion -> Some StoreRequest -> Bool
 restrictProtoVersion v (Some (BuildPaths _ _)) | v < ProtoVersion 1 30 = False