diff --git a/notmuch-client.h b/notmuch-client.h
index a220fe46..fa04fa2e 100644
--- a/notmuch-client.h
+++ b/notmuch-client.h
@@ -62,7 +62,7 @@
 #define STRINGIFY(s) STRINGIFY_(s)
 #define STRINGIFY_(s) #s
 
-struct mime_node;
+typedef struct mime_node mime_node_t;
 struct notmuch_show_params;
 
 typedef struct notmuch_show_format {
@@ -191,6 +191,12 @@ show_message_body (notmuch_message_t *message,
 notmuch_status_t
 show_one_part (const char *filename, int part);
 
+void
+format_part_json (const void *ctx, mime_node_t *node, notmuch_bool_t first);
+
+void
+format_headers_json (const void *ctx, GMimeMessage *message, notmuch_bool_t reply);
+
 char *
 json_quote_chararray (const void *ctx, const char *str, const size_t len);
 
@@ -288,7 +294,7 @@ debugger_is_active (void);
  * parts.  Message-type parts have one child, multipart-type parts
  * have multiple children, and leaf parts have zero children.
  */
-typedef struct mime_node {
+struct mime_node {
     /* The MIME object of this part.  This will be a GMimeMessage,
      * GMimePart, GMimeMultipart, or a subclass of one of these.
      *
@@ -351,7 +357,7 @@ typedef struct mime_node {
      * number to assign it (or -1 if unknown). */
     int next_child;
     int next_part_num;
-} mime_node_t;
+};
 
 /* Construct a new MIME node pointing to the root message part of
  * message.  If cryptoctx is non-NULL, it will be used to verify
diff --git a/notmuch-reply.c b/notmuch-reply.c
index f1478ccf..e2b6c253 100644
--- a/notmuch-reply.c
+++ b/notmuch-reply.c
@@ -604,6 +604,51 @@ notmuch_reply_format_default(void *ctx,
     return 0;
 }
 
+static int
+notmuch_reply_format_json(void *ctx,
+			  notmuch_config_t *config,
+			  notmuch_query_t *query,
+			  notmuch_show_params_t *params,
+			  notmuch_bool_t reply_all)
+{
+    GMimeMessage *reply;
+    notmuch_messages_t *messages;
+    notmuch_message_t *message;
+    mime_node_t *node;
+
+    if (notmuch_query_count_messages (query) != 1) {
+	fprintf (stderr, "Error: search term did not match precisely one message.\n");
+	return 1;
+    }
+
+    messages = notmuch_query_search_messages (query);
+    message = notmuch_messages_get (messages);
+    if (mime_node_open (ctx, message, params->cryptoctx, params->decrypt,
+			&node) != NOTMUCH_STATUS_SUCCESS)
+	return 1;
+
+    reply = create_reply_message (ctx, config, message, reply_all);
+    if (!reply)
+	return 1;
+
+    /* The headers of the reply message we've created */
+    printf ("{\"reply-headers\": ");
+    format_headers_json (ctx, reply, TRUE);
+    g_object_unref (G_OBJECT (reply));
+    reply = NULL;
+
+    /* Start the original */
+    printf (", \"original\": ");
+
+    format_part_json (ctx, node, TRUE);
+
+    /* End */
+    printf ("}\n");
+    notmuch_message_destroy (message);
+
+    return 0;
+}
+
 /* This format is currently tuned for a git send-email --notmuch hook */
 static int
 notmuch_reply_format_headers_only(void *ctx,
@@ -666,6 +711,7 @@ notmuch_reply_format_headers_only(void *ctx,
 
 enum {
     FORMAT_DEFAULT,
+    FORMAT_JSON,
     FORMAT_HEADERS_ONLY,
 };
 
@@ -685,6 +731,7 @@ notmuch_reply_command (void *ctx, int argc, char *argv[])
     notmuch_opt_desc_t options[] = {
 	{ NOTMUCH_OPT_KEYWORD, &format, "format", 'f',
 	  (notmuch_keyword_t []){ { "default", FORMAT_DEFAULT },
+				  { "json", FORMAT_JSON },
 				  { "headers-only", FORMAT_HEADERS_ONLY },
 				  { 0, 0 } } },
 	{ NOTMUCH_OPT_KEYWORD, &reply_all, "reply-to", 'r',
@@ -703,6 +750,8 @@ notmuch_reply_command (void *ctx, int argc, char *argv[])
 
     if (format == FORMAT_HEADERS_ONLY)
 	reply_format_func = notmuch_reply_format_headers_only;
+    else if (format == FORMAT_JSON)
+	reply_format_func = notmuch_reply_format_json;
     else
 	reply_format_func = notmuch_reply_format_default;
 
diff --git a/notmuch-show.c b/notmuch-show.c
index a7463dc8..ff9d4278 100644
--- a/notmuch-show.c
+++ b/notmuch-show.c
@@ -200,8 +200,8 @@ _is_from_line (const char *line)
 	return 0;
 }
 
-static void
-format_headers_json (const void *ctx, GMimeMessage *message)
+void
+format_headers_json (const void *ctx, GMimeMessage *message, notmuch_bool_t reply)
 {
     void *local = talloc_new (ctx);
     InternetAddressList *recipients;
@@ -225,9 +225,22 @@ format_headers_json (const void *ctx, GMimeMessage *message)
 	printf (", %s: %s",
 		json_quote_str (local, "Cc"),
 		json_quote_str (local, recipients_string));
-    printf (", %s: %s}",
-	    json_quote_str (local, "Date"),
-	    json_quote_str (local, g_mime_message_get_date_as_string (message)));
+
+    if (reply) {
+	printf (", %s: %s",
+		json_quote_str (local, "In-reply-to"),
+		json_quote_str (local, g_mime_object_get_header (GMIME_OBJECT (message), "In-reply-to")));
+
+	printf (", %s: %s",
+		json_quote_str (local, "References"),
+		json_quote_str (local, g_mime_object_get_header (GMIME_OBJECT (message), "References")));
+    } else {
+	printf (", %s: %s",
+		json_quote_str (local, "Date"),
+		json_quote_str (local, g_mime_message_get_date_as_string (message)));
+    }
+
+    printf ("}");
 
     talloc_free (local);
 }
@@ -538,7 +551,7 @@ format_part_text (const void *ctx, mime_node_t *node,
     return NOTMUCH_STATUS_SUCCESS;
 }
 
-static void
+void
 format_part_json (const void *ctx, mime_node_t *node, notmuch_bool_t first)
 {
     /* Any changes to the JSON format should be reflected in the file
@@ -549,7 +562,7 @@ format_part_json (const void *ctx, mime_node_t *node, notmuch_bool_t first)
 	format_message_json (ctx, node->envelope_file);
 
 	printf ("\"headers\": ");
-	format_headers_json (ctx, GMIME_MESSAGE (node->part));
+	format_headers_json (ctx, GMIME_MESSAGE (node->part), FALSE);
 
 	printf (", \"body\": [");
 	format_part_json (ctx, mime_node_child (node, 0), first);
@@ -623,7 +636,7 @@ format_part_json (const void *ctx, mime_node_t *node, notmuch_bool_t first)
     } else if (GMIME_IS_MESSAGE (node->part)) {
 	printf (", \"content\": [{");
 	printf ("\"headers\": ");
-	format_headers_json (local, GMIME_MESSAGE (node->part));
+	format_headers_json (local, GMIME_MESSAGE (node->part), FALSE);
 
 	printf (", \"body\": [");
 	terminator = "]}]";
diff --git a/test/multipart b/test/multipart
index e5de5d30..72d39276 100755
--- a/test/multipart
+++ b/test/multipart
@@ -613,7 +613,6 @@ EOF
 test_expect_equal_file OUTPUT EXPECTED
 
 test_begin_subtest "'notmuch reply' to a multipart message with json format"
-test_subtest_known_broken
 notmuch reply --format=json 'id:87liy5ap00.fsf@yoom.home.cworth.org' | notmuch_json_show_sanitize >OUTPUT
 cat <<EOF >EXPECTED
 {"reply-headers": {"Subject": "Re: Multipart message",