diff --git a/Command/AddComputed.hs b/Command/AddComputed.hs
index 4edce492e2..0d614a1fc0 100644
--- a/Command/AddComputed.hs
+++ b/Command/AddComputed.hs
@@ -37,14 +37,14 @@ cmd = notBareRepo $
 data AddComputedOptions = AddComputedOptions
 	{ computeParams :: CmdParams
 	, computeRemote :: DeferredParse Remote
-	, reproducible :: Reproducible
+	, reproducible :: Maybe Reproducible
 	}
 
 optParser :: CmdParamsDesc -> Parser AddComputedOptions
 optParser desc = AddComputedOptions
 	<$> cmdParams desc
 	<*> (mkParseRemoteOption <$> parseToOption)
-	<*> (fromMaybe (Reproducible False) <$> parseReproducible)
+	<*> parseReproducible
 
 newtype Reproducible = Reproducible { isReproducible :: Bool }
 
@@ -92,7 +92,7 @@ perform o r program = do
 		, Remote.Compute.computeInputs = mempty
 		, Remote.Compute.computeOutputs = mempty
 		, Remote.Compute.computeSubdir = subdir
-		, Remote.Compute.computeReproducible = isreproducible
+		, Remote.Compute.computeReproducible = False
 		}
 	fast <- Annex.getRead Annex.fast
 	starttime <- liftIO currentMonotonicTimestamp
@@ -140,7 +140,7 @@ perform o r program = do
 		| fast = do
 			addSymlink outputfile stateurlk Nothing
 			return stateurlk
-		| isreproducible = do
+		| isreproducible state = do
 			sz <- liftIO $ getFileSize outputfile'
 			metered Nothing sz Nothing $ \_ p ->
 				ingestwith $ ingestAdd p (Just ld)
@@ -170,4 +170,6 @@ perform o r program = do
 	calcduration (MonotonicTimestamp starttime) (MonotonicTimestamp endtime) =
 		fromIntegral (endtime - starttime) :: NominalDiffTime
 	
-	isreproducible = isReproducible (reproducible o)
+	isreproducible state = case reproducible o of
+		Just v -> isReproducible v
+		Nothing -> Remote.Compute.computeReproducible state
diff --git a/doc/git-annex-addcomputed.mdwn b/doc/git-annex-addcomputed.mdwn
index 9f096770b7..1da287f0cf 100644
--- a/doc/git-annex-addcomputed.mdwn
+++ b/doc/git-annex-addcomputed.mdwn
@@ -53,8 +53,11 @@ Some examples of how this might look:
 
 * `--fast`
 
-  Adds computed files to the repository, without generating their content
-  yet.
+  Adds computed files to the repository, without doing any work yet to
+  compute their content.
+
+  This implies `--unreproducible`, because even if the compute remote
+  produces reproducible output, it's not available.
 
 * `--unreproducible`, `-u`
 
@@ -70,7 +73,7 @@ Some examples of how this might look:
   Indicate that the computation is expected to be fully reproducible.
 
   This is the default when the compute remote indicates that it produces
-  reproducible output.
+  reproducible output (except when using `--fast`).
 
   If a computation turns out not to be fully reproducible, then getting
   the file from the compute remote will later fail with a checksum