diff --git a/emacs/notmuch-query.el b/emacs/notmuch-query.el
index 48acb551..592fd8f1 100644
--- a/emacs/notmuch-query.el
+++ b/emacs/notmuch-query.el
@@ -30,7 +30,7 @@ A thread is a forest or list of trees. A tree is a two element
 list where the first element is a message, and the second element
 is a possibly empty forest of replies.
 "
-  (let ((args '("show" "--format=sexp" "--format-version=3")))
+  (let ((args '("show" "--format=sexp" "--format-version=4")))
     (if notmuch-show-process-crypto
 	(setq args (append args '("--decrypt"))))
     (setq args (append args search-terms))
diff --git a/notmuch-client.h b/notmuch-client.h
index 62d4bcec..77b34184 100644
--- a/notmuch-client.h
+++ b/notmuch-client.h
@@ -145,7 +145,7 @@ chomp_newline (char *str)
  * this.  New (required) map fields can be added without increasing
  * this.
  */
-#define NOTMUCH_FORMAT_CUR 3
+#define NOTMUCH_FORMAT_CUR 4
 /* The minimum supported structured output format version.  Requests
  * for format versions below this will return an error. */
 #define NOTMUCH_FORMAT_MIN 1
diff --git a/notmuch-show.c b/notmuch-show.c
index 3ce4b63c..5c2d56e8 100644
--- a/notmuch-show.c
+++ b/notmuch-show.c
@@ -340,6 +340,48 @@ signature_status_to_string (GMimeSignatureStatus x)
     return "unknown";
 }
 
+
+/* Print signature flags */
+struct key_map_struct {
+    GMimeSignatureError bit;
+    const char * string;
+};
+
+static void
+do_format_signature_errors (sprinter_t *sp, struct key_map_struct *key_map,
+			    unsigned int array_map_len, GMimeSignatureError errors) {
+    sp->map_key (sp, "errors");
+    sp->begin_map (sp);
+
+    for (unsigned int i = 0; i < array_map_len; i++) {
+	if (errors & key_map[i].bit) {
+	    sp->map_key (sp, key_map[i].string);
+	    sp->boolean (sp, TRUE);
+	}
+    }
+
+    sp->end (sp);
+}
+
+static void
+format_signature_errors (sprinter_t *sp, GMimeSignature *signature)
+{
+    GMimeSignatureError errors = g_mime_signature_get_errors (signature);
+
+    if (errors == GMIME_SIGNATURE_ERROR_NONE)
+	return;
+
+    struct key_map_struct key_map[] = {
+	{ GMIME_SIGNATURE_ERROR_EXPSIG, "sig-expired" },
+	{ GMIME_SIGNATURE_ERROR_NO_PUBKEY, "key-missing"},
+	{ GMIME_SIGNATURE_ERROR_EXPKEYSIG, "key-expired"},
+	{ GMIME_SIGNATURE_ERROR_REVKEYSIG, "key-revoked"},
+	{ GMIME_SIGNATURE_ERROR_UNSUPP_ALGO, "alg-unsupported"},
+    };
+
+    do_format_signature_errors (sp, key_map, ARRAY_SIZE(key_map), errors);
+}
+
 /* Signature status sprinter (GMime 2.6) */
 static void
 format_part_sigstatus_sprinter (sprinter_t *sp, mime_node_t *node)
@@ -404,10 +446,14 @@ format_part_sigstatus_sprinter (sprinter_t *sp, mime_node_t *node)
 	    }
 	}
 
-	GMimeSignatureError errors = g_mime_signature_get_errors (signature);
-	if (errors != GMIME_SIGNATURE_ERROR_NONE) {
-	    sp->map_key (sp, "errors");
-	    sp->integer (sp, errors);
+	if (notmuch_format_version <= 3) {
+	    GMimeSignatureError errors = g_mime_signature_get_errors (signature);
+	    if (errors != GMIME_SIGNATURE_ERROR_NONE) {
+		sp->map_key (sp, "errors");
+		sp->integer (sp, errors);
+	    }
+	} else {
+	    format_signature_errors (sp, signature);
 	}
 
 	sp->end (sp);
diff --git a/test/T350-crypto.sh b/test/T350-crypto.sh
index d21cad14..0753acf3 100755
--- a/test/T350-crypto.sh
+++ b/test/T350-crypto.sh
@@ -123,7 +123,7 @@ expected='[[[{"id": "XXXXX",
  "body": [{"id": 1,
  "sigstatus": [{"status": "error",
  "keyid": "'$(echo $FINGERPRINT | cut -c 25-)'",
- "errors": 2}],
+ "errors": {"key-missing": true}}],
  "content-type": "multipart/signed",
  "content": [{"id": 2,
  "content-type": "text/plain",
@@ -367,7 +367,7 @@ expected='[[[{"id": "XXXXX",
  "body": [{"id": 1,
  "sigstatus": [{"status": "error",
  "keyid": "6D92612D94E46381",
- "errors": 8}],
+ "errors": {"key-revoked": true}}],
  "content-type": "multipart/signed",
  "content": [{"id": 2,
  "content-type": "text/plain",
diff --git a/test/T355-smime.sh b/test/T355-smime.sh
index 0f39bc69..03d24581 100755
--- a/test/T355-smime.sh
+++ b/test/T355-smime.sh
@@ -64,8 +64,8 @@ expected='[[[{"id": "XXXXX",
  "To": "test_suite@notmuchmail.org",
  "Date": "Sat, 01 Jan 2000 12:00:00 +0000"},
  "body": [{"id": 1,
- "sigstatus": [{"status": "good",
- "fingerprint": "'$FINGERPRINT'",
+ "sigstatus": [{"fingerprint": "'$FINGERPRINT'",
+ "status": "good",
  "expires": 424242424,
  "created": 946728000}],
  "content-type": "multipart/signed",
diff --git a/test/T450-emacs-show.sh b/test/T450-emacs-show.sh
index d302efb6..c4bc5ce0 100755
--- a/test/T450-emacs-show.sh
+++ b/test/T450-emacs-show.sh
@@ -191,7 +191,7 @@ This is an error (see *Notmuch errors* for more details)
 === ERROR ===
 [XXX]
 This is an error
-command: YYY/notmuch_fail show --format\\=sexp --format-version\\=3 --exclude\\=false \\' \\* \\'
+command: YYY/notmuch_fail show --format\\=sexp --format-version\\=4 --exclude\\=false \\' \\* \\'
 exit status: 1
 stderr:
 This is an error