diff --git a/CHANGES b/CHANGES
index 234cd9e44..1a5e63a3d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -16,6 +16,8 @@ Features added
 Bugs fixed
 ----------
 
+* #5418: Incorrect default path for sphinx-build -d/doctrees files
+
 Testing
 --------
 
diff --git a/sphinx/cmd/build.py b/sphinx/cmd/build.py
index 7fc12e78a..35176c7fc 100644
--- a/sphinx/cmd/build.py
+++ b/sphinx/cmd/build.py
@@ -219,7 +219,7 @@ def build_main(argv=sys.argv[1:]):  # type: ignore
         args.confdir = args.sourcedir
 
     if not args.doctreedir:
-        args.doctreedir = os.path.join(args.sourcedir, '.doctrees')
+        args.doctreedir = os.path.join(args.outputdir, '.doctrees')
 
     # handle remaining filename arguments
     filenames = args.filenames