--- a/src/doveadm/dsync/doveadm-dsync.c	Mon Sep 15 11:19:50 2014 +0300
+++ b/src/doveadm/dsync/doveadm-dsync.c	Mon Sep 15 18:02:02 2014 +0300
@@ -541,6 +541,7 @@
 	memcpy(set.sync_box_guid, ctx->mailbox_guid, sizeof(set.sync_box_guid));
 	set.lock_timeout_secs = ctx->lock_timeout;
 	set.state = ctx->state_input;
+	set.mailbox_alt_char = doveadm_settings->dsync_alt_char[0];
 	if (array_count(&ctx->exclude_mailboxes) > 0) {
 		/* array is NULL-terminated in init() */
 		set.exclude_mailboxes = array_idx(&ctx->exclude_mailboxes, 0);

--- a/src/doveadm/dsync/dsync-brain-mailbox-tree.c	Mon Sep 15 11:19:50 2014 +0300
+++ b/src/doveadm/dsync/dsync-brain-mailbox-tree.c	Mon Sep 15 18:02:02 2014 +0300
@@ -3,7 +3,6 @@
 #include "lib.h"
 #include "str.h"
 #include "mail-namespace.h"
-#include "doveadm-settings.h"
 #include "dsync-ibc.h"
 #include "dsync-mailbox-tree.h"
 #include "dsync-brain-private.h"
@@ -47,12 +46,10 @@
 	dsync_brain_check_namespaces(brain);
 
 	brain->local_mailbox_tree =
-		dsync_mailbox_tree_init(brain->hierarchy_sep,
-					doveadm_settings->dsync_alt_char[0]);
+		dsync_mailbox_tree_init(brain->hierarchy_sep, brain->alt_char);
 	/* we'll convert remote mailbox names to use our own separator */
 	brain->remote_mailbox_tree =
-		dsync_mailbox_tree_init(brain->hierarchy_sep,
-					doveadm_settings->dsync_alt_char[0]);
+		dsync_mailbox_tree_init(brain->hierarchy_sep, brain->alt_char);
 
 	/* fill the local mailbox tree */
 	for (ns = brain->user->namespaces; ns != NULL; ns = ns->next) {
@@ -238,7 +235,7 @@
 	struct mail_namespace *ns;
 	const char *p;
 	string_t *vname;
-	char ns_sep, alt_char = doveadm_settings->dsync_alt_char[0];
+	char ns_sep;
 
 	i_assert(*name_parts != NULL);
 
@@ -254,13 +251,13 @@
 			if (*p != ns_sep)
 				str_append_c(vname, *p);
 			else
-				str_append_c(vname, alt_char);
+				str_append_c(vname, brain->alt_char);
 		}
 		str_append_c(vname, ns_sep);
 	}
 	str_truncate(vname, str_len(vname)-1);
 
-	dsync_fix_mailbox_name(ns, vname, alt_char);
+	dsync_fix_mailbox_name(ns, vname, brain->alt_char);
 	*name_r = str_c(vname);
 	*ns_r = ns;
 	return 0;

--- a/src/doveadm/dsync/dsync-brain-private.h	Mon Sep 15 11:19:50 2014 +0300
+++ b/src/doveadm/dsync/dsync-brain-private.h	Mon Sep 15 18:02:02 2014 +0300
@@ -55,6 +55,7 @@
 	guid_128_t sync_box_guid;
 	const char *const *exclude_mailboxes;
 	enum dsync_brain_sync_type sync_type;
+	char alt_char;
 
 	unsigned int lock_timeout;
 	int lock_fd;

--- a/src/doveadm/dsync/dsync-brain.c	Mon Sep 15 11:19:50 2014 +0300
+++ b/src/doveadm/dsync/dsync-brain.c	Mon Sep 15 18:02:02 2014 +0300
@@ -171,6 +171,8 @@
 		}
 		str_delete(sync_ns_str, str_len(sync_ns_str)-1, 1);
 	}
+	brain->alt_char = set->mailbox_alt_char == '\0' ? '_' :
+		set->mailbox_alt_char;
 	brain->sync_box = p_strdup(brain->pool, set->sync_box);
 	brain->exclude_mailboxes = set->exclude_mailboxes == NULL ? NULL :
 		p_strarray_dup(brain->pool, set->exclude_mailboxes);

--- a/src/doveadm/dsync/dsync-brain.h	Mon Sep 15 11:19:50 2014 +0300
+++ b/src/doveadm/dsync/dsync-brain.h	Mon Sep 15 18:02:02 2014 +0300
@@ -48,6 +48,9 @@
 	/* Exclude these mailboxes from the sync. They can contain '*'
 	   wildcards and be \special-use flags. */
 	const char *const *exclude_mailboxes;
+	/* Alternative character to use in mailbox names where the original
+	   character cannot be used. */
+	char mailbox_alt_char;
 
 	/* If non-zero, use dsync lock file for this user */
 	unsigned int lock_timeout_secs;

--- a/src/doveadm/dsync/dsync-mailbox-tree.c	Mon Sep 15 11:19:50 2014 +0300
+++ b/src/doveadm/dsync/dsync-mailbox-tree.c	Mon Sep 15 18:02:02 2014 +0300
@@ -4,7 +4,6 @@
 #include "array.h"
 #include "hash.h"
 #include "str.h"
-#include "doveadm-settings.h"
 #include "mailbox-list-private.h"
 #include "dsync-mailbox-tree-private.h"