diff --git a/Annex/VariantFile.hs b/Annex/VariantFile.hs
index 7eee545ec7..acab1e8281 100644
--- a/Annex/VariantFile.hs
+++ b/Annex/VariantFile.hs
@@ -10,6 +10,8 @@ module Annex.VariantFile where
 import Annex.Common
 import Utility.Hash
 
+import qualified Data.ByteString.Lazy as L
+
 variantMarker :: String
 variantMarker = ".variant-"
 
@@ -34,10 +36,10 @@ mkVariant file variant = takeDirectory file
  -}
 variantFile :: FilePath -> Key -> FilePath
 variantFile file key
-	| doubleconflict = mkVariant file (serializeKey key)
-	| otherwise = mkVariant file (shortHash $ serializeKey key)
+	| doubleconflict = mkVariant file (keyFile key)
+	| otherwise = mkVariant file (shortHash $ serializeKey' key)
   where
 	doubleconflict = variantMarker `isInfixOf` file
 
-shortHash :: String -> String
-shortHash = take 4 . show . md5 . encodeBL
+shortHash :: L.ByteString -> String
+shortHash = take 4 . show . md5
diff --git a/CHANGELOG b/CHANGELOG
index 21c7d5c4e2..e44ee49d0d 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -27,6 +27,8 @@ git-annex (7.20181212) UNRELEASED; urgency=medium
   * Improve uuid.log parser to preserve whitespace in repo descriptions.
   * Improve activity.log parser to not remove unknown values,
     allowing for future expansion.
+  * addunused, merge, assistant: Avoid creating work tree files in
+    subdirectories in an edge case where the key contains "/".
 
  -- Joey Hess <id@joeyh.name>  Tue, 18 Dec 2018 12:24:52 -0400
 
diff --git a/Command/AddUnused.hs b/Command/AddUnused.hs
index 0ac2316122..b07d2ba20f 100644
--- a/Command/AddUnused.hs
+++ b/Command/AddUnused.hs
@@ -32,7 +32,7 @@ perform key = next $ do
 	addLink file key Nothing
 	return True
   where
-	file = "unused." ++ serializeKey key
+	file = "unused." ++ keyFile key
 
 {- The content is not in the annex, but in another directory, and
  - it seems better to error out, rather than moving bad/tmp content into