diff --git a/emacs/notmuch-address.el b/emacs/notmuch-address.el
index 74a4584f..f937e708 100644
--- a/emacs/notmuch-address.el
+++ b/emacs/notmuch-address.el
@@ -317,7 +317,7 @@ execution, CALLBACK is called when harvesting finishes."
 			    (when config-query
 			      (format " and (%s)" config-query)))
 		  from-or-to-me-query))
-	 (args `("address" "--format=sexp" "--format-version=3"
+	 (args `("address" "--format=sexp" "--format-version=4"
 		 ,(if sent "--output=recipients" "--output=sender")
 		 "--deduplicate=address"
 		 ,query)))
diff --git a/emacs/notmuch-mua.el b/emacs/notmuch-mua.el
index ddfb9811..fd64b362 100644
--- a/emacs/notmuch-mua.el
+++ b/emacs/notmuch-mua.el
@@ -176,7 +176,7 @@ mutiple parts get a header."
   (unless (bolp) (insert "\n")))
 
 (defun notmuch-mua-reply (query-string &optional sender reply-all)
-  (let ((args '("reply" "--format=sexp" "--format-version=3"))
+  (let ((args '("reply" "--format=sexp" "--format-version=4"))
 	(process-crypto notmuch-show-process-crypto)
 	reply
 	original)
diff --git a/emacs/notmuch-tree.el b/emacs/notmuch-tree.el
index 55212626..022525ae 100644
--- a/emacs/notmuch-tree.el
+++ b/emacs/notmuch-tree.el
@@ -917,7 +917,7 @@ the same as for the function notmuch-tree."
     (notmuch-tag-clear-cache)
     (let ((proc (notmuch-start-notmuch
 		 "notmuch-tree" (current-buffer) #'notmuch-tree-process-sentinel
-		 "show" "--body=false" "--format=sexp" "--format-version=3"
+		 "show" "--body=false" "--format=sexp" "--format-version=4"
 		 message-arg search-args))
 	  ;; Use a scratch buffer to accumulate partial output.
 	  ;; This buffer will be killed by the sentinel, which
diff --git a/emacs/notmuch.el b/emacs/notmuch.el
index bd503a11..0aeff560 100644
--- a/emacs/notmuch.el
+++ b/emacs/notmuch.el
@@ -994,7 +994,7 @@ the configured default sort order."
       (save-excursion
 	(let ((proc (notmuch-start-notmuch
 		     "notmuch-search" buffer #'notmuch-search-process-sentinel
-		     "search" "--format=sexp" "--format-version=3"
+		     "search" "--format=sexp" "--format-version=4"
 		     (if oldest-first
 			 "--sort=oldest-first"
 		       "--sort=newest-first")
diff --git a/test/T310-emacs.sh b/test/T310-emacs.sh
index c8a25de2..fde11790 100755
--- a/test/T310-emacs.sh
+++ b/test/T310-emacs.sh
@@ -1015,7 +1015,7 @@ YYY/notmuch_fail exited with status 1 (see *Notmuch errors* for more details)
 === ERROR ===
 [XXX]
 YYY/notmuch_fail exited with status 1
-command: YYY/notmuch_fail search --format\=sexp --format-version\=3 --sort\=newest-first tag\:inbox
+command: YYY/notmuch_fail search --format\=sexp --format-version\=4 --sort\=newest-first tag\:inbox
 exit status: 1"
 
 test_begin_subtest "Search handles subprocess warnings"