diff --git a/CHANGELOG b/CHANGELOG
index bf4b7fe36d..ab8e557dca 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -4,6 +4,8 @@ git-annex (10.20231130) UNRELEASED; urgency=medium
     remote.foo.annex-ignore, as documented.
   * Support git-annex copy/move --from-anywhere --to remote.
   * sync: Fix locking problems during merge when annex.pidlock is set.
+  * Avoid a problem with temp file names ending in "." on certian
+    filesystems that have problems with such filenames.
 
  -- Joey Hess <id@joeyh.name>  Thu, 30 Nov 2023 14:48:12 -0400
 
diff --git a/Utility/Tmp.hs b/Utility/Tmp.hs
index efb15bd9b3..75048fcd8f 100644
--- a/Utility/Tmp.hs
+++ b/Utility/Tmp.hs
@@ -35,8 +35,10 @@ type Template = String
  - to help identify what call was responsible.
  -}
 openTmpFileIn :: FilePath -> String -> IO (FilePath, Handle)
-openTmpFileIn dir template = openTempFile dir template
-	`catchIO` decoraterrror
+openTmpFileIn dir template = do
+	liftIO $ print ("openTmpFileIn", dir, template)
+	openTempFile dir template
+		`catchIO` decoraterrror
   where
 	decoraterrror e = throwM $
 		let loc = ioeGetLocation e ++ " template " ++ template
@@ -105,7 +107,12 @@ withTmpFileIn tmpdir template a = bracket create remove use
  -}
 relatedTemplate :: FilePath -> FilePath
 relatedTemplate f
-	| len > 20 = truncateFilePath (len - 20) f
+	| len > 20 = 
+		{- Some filesystems like FAT have issues with filenames
+		 - ending in ".", so avoid truncating a filename to end
+		 - that way. -}
+		reverse $ dropWhile (== '.') $ reverse $
+			truncateFilePath (len - 20) f
 	| otherwise = f
   where
 	len = length f
diff --git a/doc/bugs/Invalid_argument_saving_FreeSurfer_file_on_NTFS.mdwn b/doc/bugs/Invalid_argument_saving_FreeSurfer_file_on_NTFS.mdwn
index 5b4e7db549..241ee8ce8c 100644
--- a/doc/bugs/Invalid_argument_saving_FreeSurfer_file_on_NTFS.mdwn
+++ b/doc/bugs/Invalid_argument_saving_FreeSurfer_file_on_NTFS.mdwn
@@ -91,3 +91,5 @@ add: 1 failed
 ### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)
 
 Yes! I use git annex and datalad all the time for personal and work projects. 
+
+> [[fixed|done]] --[[Joey]]
diff --git a/doc/bugs/Invalid_argument_saving_FreeSurfer_file_on_NTFS/comment_1_181a319138cc10742bc8676d77e8a614._comment b/doc/bugs/Invalid_argument_saving_FreeSurfer_file_on_NTFS/comment_1_181a319138cc10742bc8676d77e8a614._comment
new file mode 100644
index 0000000000..0ab08545f2
--- /dev/null
+++ b/doc/bugs/Invalid_argument_saving_FreeSurfer_file_on_NTFS/comment_1_181a319138cc10742bc8676d77e8a614._comment
@@ -0,0 +1,16 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 1"""
+ date="2023-12-05T16:16:35Z"
+ content="""
+This is EINVAL from probably open(2) or something like that.
+
+       EINVAL The  final  component ("basename") of pathname is invalid (e.g.,
+              it contains characters not permitted by the underlying  filesys‐
+              tem).
+
+The problem is likely the ending ".", since FAT and probably other Microsoft filesystems
+don't allow that, and/or have other strange behavior like silently removing that.
+
+Changed the code to avoid this.
+"""]]