diff --git a/lib/config.cc b/lib/config.cc
index 4c0cfe92..948751bc 100644
--- a/lib/config.cc
+++ b/lib/config.cc
@@ -390,6 +390,8 @@ _notmuch_config_key_to_string (notmuch_config_key_t key) {
     switch (key) {
     case NOTMUCH_CONFIG_DATABASE_PATH:
 	return "database.path";
+    case NOTMUCH_CONFIG_HOOK_DIR:
+	return "database.hook_dir";
     case NOTMUCH_CONFIG_EXCLUDE_TAGS:
 	return "search.exclude_tags";
     case NOTMUCH_CONFIG_NEW_TAGS:
@@ -428,6 +430,7 @@ _notmuch_config_default (void *ctx, notmuch_config_key_t key) {
 	return "inbox;unread";
     case NOTMUCH_CONFIG_SYNC_MAILDIR_FLAGS:
 	return "true";
+    case NOTMUCH_CONFIG_HOOK_DIR:
     case NOTMUCH_CONFIG_NEW_IGNORE:
     case NOTMUCH_CONFIG_USER_NAME:
     case NOTMUCH_CONFIG_PRIMARY_EMAIL:
diff --git a/lib/notmuch.h b/lib/notmuch.h
index 5e07a01a..5a5d99c0 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -2460,6 +2460,7 @@ notmuch_config_list_destroy (notmuch_config_list_t *config_list);
 typedef enum _notmuch_config_key {
     NOTMUCH_CONFIG_FIRST,
     NOTMUCH_CONFIG_DATABASE_PATH = NOTMUCH_CONFIG_FIRST,
+    NOTMUCH_CONFIG_HOOK_DIR,
     NOTMUCH_CONFIG_EXCLUDE_TAGS,
     NOTMUCH_CONFIG_NEW_TAGS,
     NOTMUCH_CONFIG_NEW_IGNORE,
diff --git a/test/T590-libconfig.sh b/test/T590-libconfig.sh
index 4edc53f1..e2050b50 100755
--- a/test/T590-libconfig.sh
+++ b/test/T590-libconfig.sh
@@ -333,6 +333,7 @@ EOF
 cat <<'EOF' >EXPECTED
 == stdout ==
 MAIL_DIR
+NULL
 
 inbox;unread
 NULL