diff --git a/Messages/Progress.hs b/Messages/Progress.hs
index 48cc4912d3..da60716e64 100644
--- a/Messages/Progress.hs
+++ b/Messages/Progress.hs
@@ -116,7 +116,10 @@ metered' st othermeter msize showoutput a = go st
 			a meter (combinemeter m)
 		| otherwise = nometer
 	go (MessageState { outputType = SerializedOutput h _ }) = do
-		liftIO $ outputSerialized h $ BeginProgressMeter msize
+		liftIO $ outputSerialized h BeginProgressMeter
+		case msize of
+			Just sz -> liftIO $ outputSerialized h $ UpdateProgressMeterTotalSize sz
+			Nothing -> noop
 		szv <- liftIO $ newIORef msize
 		meter <- liftIO $ mkMeter msize $ \_ msize' _old new -> do
 			case msize' of
diff --git a/Messages/Serialized.hs b/Messages/Serialized.hs
index cd62e10448..ff2517a901 100644
--- a/Messages/Serialized.hs
+++ b/Messages/Serialized.hs
@@ -63,11 +63,11 @@ relaySerializedOutput getso sendsor meterreport runannex = go Nothing
 					outputSerialized h $ JSONObject b
 				_ -> q
 			loop st
-		Left (BeginProgressMeter sz) -> do
+		Left BeginProgressMeter -> do
 			ost <- runannex (Annex.getState Annex.output)
 			-- Display a progress meter while running, until
 			-- the meter ends or a final value is returned.
-			metered' ost Nothing sz (runannex showOutput) 
+			metered' ost Nothing Nothing (runannex showOutput) 
 				(\meter meterupdate -> loop (Just (meter, meterupdate)))
 				>>= \case
 					Right r -> return (Right r)
diff --git a/Types/Messages.hs b/Types/Messages.hs
index ffb85ac3d0..593207be35 100644
--- a/Types/Messages.hs
+++ b/Types/Messages.hs
@@ -68,9 +68,9 @@ newMessageState = do
 data SerializedOutput
 	= OutputMessage S.ByteString
 	| OutputError String
-	| BeginProgressMeter (Maybe TotalSize)
-	| UpdateProgressMeter BytesProcessed
+	| BeginProgressMeter
 	| UpdateProgressMeterTotalSize TotalSize
+	| UpdateProgressMeter BytesProcessed
 	| EndProgressMeter
 	| BeginPrompt
 	| EndPrompt
diff --git a/Types/Transferrer.hs b/Types/Transferrer.hs
index 7dbcfb23be..79b0895126 100644
--- a/Types/Transferrer.hs
+++ b/Types/Transferrer.hs
@@ -85,14 +85,12 @@ instance Proto.Sendable TransferResponse where
 		["om", Proto.serialize (encode_c (decodeBS m))]
 	formatMessage (TransferOutput (OutputError e)) =
 		["oe", Proto.serialize (encode_c e)]
-	formatMessage (TransferOutput (BeginProgressMeter (Just (TotalSize n)))) =
-		["opb", Proto.serialize n]
-	formatMessage (TransferOutput (BeginProgressMeter Nothing)) =
-		["opbx"]
-	formatMessage (TransferOutput (UpdateProgressMeter n)) =
-		["op", Proto.serialize n]
+	formatMessage (TransferOutput BeginProgressMeter) =
+		["opb"]
 	formatMessage (TransferOutput (UpdateProgressMeterTotalSize (TotalSize sz))) =
 		["ops", Proto.serialize sz]
+	formatMessage (TransferOutput (UpdateProgressMeter n)) =
+		["op", Proto.serialize n]
 	formatMessage (TransferOutput EndProgressMeter) =
 		["ope"]
 	formatMessage (TransferOutput BeginPrompt) =
@@ -111,14 +109,12 @@ instance Proto.Receivable TransferResponse where
 		TransferOutput . OutputMessage . encodeBS . decode_c
 	parseCommand "oe" = Proto.parse1 $
 		TransferOutput . OutputError . decode_c
-	parseCommand "opb" = Proto.parse1 $
-		TransferOutput . BeginProgressMeter . Just . TotalSize
-	parseCommand "opbx" = Proto.parse0 $
-		TransferOutput (BeginProgressMeter Nothing)
-	parseCommand "op" = Proto.parse1 $
-		TransferOutput . UpdateProgressMeter
+	parseCommand "opb" = Proto.parse0 $
+		TransferOutput BeginProgressMeter
 	parseCommand "ops" = Proto.parse1 $
 		TransferOutput . UpdateProgressMeterTotalSize . TotalSize
+	parseCommand "op" = Proto.parse1 $
+		TransferOutput . UpdateProgressMeter
 	parseCommand "ope" = Proto.parse0 $
 		TransferOutput EndProgressMeter
 	parseCommand "oprb" = Proto.parse0 $