diff --git a/Annex/Drop.hs b/Annex/Drop.hs
index b7543ec794..6f55378719 100644
--- a/Annex/Drop.hs
+++ b/Annex/Drop.hs
@@ -103,16 +103,12 @@ handleDropsFrom locs rs reason fromhere key afile si preverified runner = do
 			dropr fs r n >>= go fs rest
 		| otherwise = pure n
 
-	checkdrop fs n u a
-		| null fs = check $ -- no associated files; unused content
-			wantDrop True u (Just key) (AssociatedFile Nothing)
-		| otherwise = check $
-			allM (wantDrop True u (Just key) . AssociatedFile . Just) fs
-		where
-			check c = ifM c
-				( dodrop n u a
-				, return n
-				)
+	checkdrop fs n u a =
+		let afs = map (AssociatedFile . Just) fs
+		in ifM (wantDrop True u (Just key) afile (Just afs))
+			( dodrop n u a
+			, return n
+			)
 
 	dodrop n@(have, numcopies, mincopies, _untrusted) u a = 
 		ifM (safely $ runner $ a numcopies mincopies)
diff --git a/Annex/Wanted.hs b/Annex/Wanted.hs
index 021fe5cafb..a1ac7b20c4 100644
--- a/Annex/Wanted.hs
+++ b/Annex/Wanted.hs
@@ -1,6 +1,6 @@
 {- git-annex checking whether content is wanted
  -
- - Copyright 2012 Joey Hess <id@joeyh.name>
+ - Copyright 2012-2021 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -10,6 +10,9 @@ module Annex.Wanted where
 import Annex.Common
 import Logs.PreferredContent
 import Annex.UUID
+import Annex.CatFile
+import Git.FilePath
+import qualified Database.Keys
 
 import qualified Data.Set as S
 
@@ -22,8 +25,40 @@ wantSend :: Bool -> Maybe Key -> AssociatedFile -> UUID -> Annex Bool
 wantSend d key file to = isPreferredContent (Just to) S.empty key file d
 
 {- Check if a file can be dropped, maybe from a remote.
- - Don't drop files that are preferred content. -}
-wantDrop :: Bool -> Maybe UUID -> Maybe Key -> AssociatedFile -> Annex Bool
-wantDrop d from key file = do
-	u <- maybe getUUID (return . id) from
-	not <$> isPreferredContent (Just u) (S.singleton u) key file d
+ - Don't drop files that are preferred content.
+ -
+ - The AssociatedFile is the one that the user requested to drop.
+ - There may be other files that use the same key, and preferred content
+ - may match some of those and not others. If any are preferred content,
+ - that will prevent dropping. When the other associated files are known,
+ - they can be provided, otherwise this looks them up.
+ -}
+wantDrop :: Bool -> Maybe UUID -> Maybe Key -> AssociatedFile -> (Maybe [AssociatedFile]) -> Annex Bool
+wantDrop d from key file others = do
+	u <- maybe getUUID (pure . id) from
+	let s = S.singleton u
+	let checkwant f = isPreferredContent (Just u) s key f d
+	ifM (checkwant file)
+		( return False
+		, do
+			others' <- case others of
+				Just afs -> pure (filter (/= file) afs)
+				Nothing -> case key of
+					Just k -> mapM (\f -> AssociatedFile . Just <$> fromRepo (fromTopFilePath f))
+						=<< Database.Keys.getAssociatedFiles k
+					Nothing -> pure []
+			l <- filterM checkwant others'
+			if null l
+				then return True
+				else checkassociated l
+		)
+  where
+	-- Some associated files that are in the keys database may no
+	-- longer correspond to files in the repository, and should
+	-- not prevent dropping.
+	checkassociated [] = return True
+	checkassociated (AssociatedFile (Just af):fs) =
+		catKeyFile af >>= \case
+			Just k | Just k == key -> return False
+			_ -> checkassociated fs
+	checkassociated (AssociatedFile Nothing:fs) = checkassociated fs
diff --git a/CHANGELOG b/CHANGELOG
index b00b6ae1a6..4fc140d15c 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,9 @@
 git-annex (8.20210429) UNRELEASED; urgency=medium
 
+  * drop: When two files have the same content, and a preferred content
+    expression matches one but not the other, do not drop the file.
+  * sync --content, assistant: Fix an edge case where a file that is not
+    preferred content did not get dropped.
   * filter-branch: New command, useful to produce a filtered version of the
     git-annex branch, eg when splitting a repository.
   * fromkey: Create an unlocked file when used in an adjusted branch
diff --git a/Command/Drop.hs b/Command/Drop.hs
index 26a16fdd37..6422fc26d5 100644
--- a/Command/Drop.hs
+++ b/Command/Drop.hs
@@ -86,13 +86,13 @@ start o from si file key = start' o from key afile ai si
 start' :: DropOptions -> Maybe Remote -> Key -> AssociatedFile -> ActionItem -> SeekInput -> CommandStart
 start' o from key afile ai si = 
 	checkDropAuto (autoMode o) from afile key $ \numcopies mincopies ->
-		stopUnless want $
+		stopUnless wantdrop $
 			case from of
 				Nothing -> startLocal afile ai si numcopies mincopies key []
 				Just remote -> startRemote afile ai si numcopies mincopies key remote
   where
-	want
-		| autoMode o = wantDrop False (Remote.uuid <$> from) (Just key) afile
+	wantdrop
+		| autoMode o = wantDrop False (Remote.uuid <$> from) (Just key) afile Nothing
 		| otherwise = return True
 
 startKeys :: DropOptions -> Maybe Remote -> (SeekInput, Key, ActionItem) -> CommandStart
diff --git a/Limit/Wanted.hs b/Limit/Wanted.hs
index 5518fa0bc9..9188594b90 100644
--- a/Limit/Wanted.hs
+++ b/Limit/Wanted.hs
@@ -19,7 +19,7 @@ addWantGet = addPreferredContentLimit $
 
 addWantDrop :: Annex ()
 addWantDrop = addPreferredContentLimit $
-	checkWant $ wantDrop False Nothing Nothing
+	checkWant $ \af -> wantDrop False Nothing Nothing af (Just [])
 
 addPreferredContentLimit :: (MatchInfo -> Annex Bool) -> Annex ()
 addPreferredContentLimit a = do
diff --git a/doc/bugs/indeterminite_preferred_content_state_for_duplicated_file.mdwn b/doc/bugs/indeterminite_preferred_content_state_for_duplicated_file.mdwn
index 0ca978dd3b..ee0d5a3930 100644
--- a/doc/bugs/indeterminite_preferred_content_state_for_duplicated_file.mdwn
+++ b/doc/bugs/indeterminite_preferred_content_state_for_duplicated_file.mdwn
@@ -19,3 +19,5 @@ So, this seems solvable in v7 repositories, but not in v5.
 Also, the associated files map may not be accurate at all times, so that's
 a wrinkle to using it for this. Also, only unlocked files get into the
 associated files map. --[[Joey]]
+
+> [[fixed|done]] --[[Joey]]
diff --git a/doc/git-annex-matching-options.mdwn b/doc/git-annex-matching-options.mdwn
index d2104c7ccf..fc7b794f4c 100644
--- a/doc/git-annex-matching-options.mdwn
+++ b/doc/git-annex-matching-options.mdwn
@@ -141,6 +141,11 @@ in either of two repositories.
   make it want to drop. Note that this will match even files that have
   already been dropped, unless limited with e.g., `--in .`
 
+  Files that this matches will not necessarily be dropped by
+  `git-annex drop --auto`. This does not check that there are enough copies
+  to drop. Also the same content may be used by a file that is not wanted
+  to be dropped.
+
 * `--accessedwithin=interval`
 
   Matches files that were accessed recently, within the specified time