diff --git a/coreapi/chat.c b/coreapi/chat.c
index abbbbf745..0140bdbe1 100644
--- a/coreapi/chat.c
+++ b/coreapi/chat.c
@@ -400,6 +400,7 @@ static LinphoneChatRoom * _linphone_core_create_chat_room(LinphoneCore *lc, Linp
 	cr->lc = lc;
 	cr->peer = linphone_address_as_string(addr);
 	cr->peer_url = addr;
+	cr->unread_count = -1;
 	lc->chatrooms = ms_list_append(lc->chatrooms, (void *)cr);
 	return cr;
 }
@@ -619,6 +620,8 @@ static void _linphone_chat_room_send_message(LinphoneChatRoom *cr, LinphoneChatM
 	msg->dir=LinphoneChatMessageOutgoing;
 	msg->from=linphone_address_new(identity);
 	msg->storage_id=linphone_chat_message_store(msg);
+	
+	if(cr->unread_count >= 0 && !msg->is_read) cr->unread_count++;
 
 	// add to transient list
 	cr->transient_messages = ms_list_append(cr->transient_messages, linphone_chat_message_ref(msg));
@@ -772,6 +775,10 @@ void linphone_core_message_received(LinphoneCore *lc, SalOp *op, const SalMessag
 
 	linphone_address_destroy(addr);
 	msg->storage_id=linphone_chat_message_store(msg);
+	
+	if(cr->unread_count < 0) cr->unread_count = 1;
+	else cr->unread_count++;
+	
 	linphone_chat_room_message_received(cr,lc,msg);
 	linphone_chat_message_unref(msg);
 }
diff --git a/coreapi/message_storage.c b/coreapi/message_storage.c
index 22da7b8d0..a5985f4d3 100644
--- a/coreapi/message_storage.c
+++ b/coreapi/message_storage.c
@@ -38,6 +38,7 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 #define MAX_PATH_SIZE 1024
 
 #include "sqlite3.h"
+#include <assert.h>
 
 static ORTP_INLINE LinphoneChatMessage* get_transient_message(LinphoneChatRoom* cr, unsigned int storage_id){
 	MSList* transients = cr->transient_messages;
@@ -286,6 +287,9 @@ void linphone_chat_room_mark_as_read(LinphoneChatRoom *cr){
 	char *buf;
 
 	if (lc->db==NULL) return ;
+	
+	// optimization: do not modify the database if no message is marked as unread
+	if(linphone_chat_room_get_unread_messages_count(cr) == 0) return;
 
 	peer=linphone_address_as_string_uri_only(linphone_chat_room_get_peer_address(cr));
 	buf=sqlite3_mprintf("UPDATE history SET read=%i WHERE remoteContact = %Q;",
@@ -293,6 +297,8 @@ void linphone_chat_room_mark_as_read(LinphoneChatRoom *cr){
 	linphone_sql_request(lc->db,buf);
 	sqlite3_free(buf);
 	ms_free(peer);
+	
+	cr->unread_count = 0;
 }
 
 void linphone_chat_room_update_url(LinphoneChatRoom *cr, LinphoneChatMessage *msg) {
@@ -315,6 +321,9 @@ static int linphone_chat_room_get_messages_count(LinphoneChatRoom *cr, bool_t un
 	int returnValue;
 
 	if (lc->db==NULL) return 0;
+	
+	// optimization: do not read database if the count is already available in memory
+	if(unread_only && cr->unread_count >= 0) return cr->unread_count;
 
 	peer=linphone_address_as_string_uri_only(linphone_chat_room_get_peer_address(cr));
 	buf=sqlite3_mprintf("SELECT count(*) FROM history WHERE remoteContact = %Q %s;",peer,unread_only?"AND read = 0":"");
@@ -327,6 +336,11 @@ static int linphone_chat_room_get_messages_count(LinphoneChatRoom *cr, bool_t un
 	sqlite3_finalize(selectStatement);
 	sqlite3_free(buf);
 	ms_free(peer);
+	
+	/* no need to test the sign of cr->unread_count here
+	 * because it has been tested above */
+	if(unread_only) cr->unread_count = numrows;
+	
 	return numrows;
 }
 
@@ -347,6 +361,11 @@ void linphone_chat_room_delete_message(LinphoneChatRoom *cr, LinphoneChatMessage
 	buf=sqlite3_mprintf("DELETE FROM history WHERE id = %i;", msg->storage_id);
 	linphone_sql_request(lc->db,buf);
 	sqlite3_free(buf);
+	
+	if(cr->unread_count >= 0 && !msg->is_read) {
+		assert(cr->unread_count > 0);
+		cr->unread_count--;
+	}
 }
 
 void linphone_chat_room_delete_history(LinphoneChatRoom *cr){
@@ -361,6 +380,8 @@ void linphone_chat_room_delete_history(LinphoneChatRoom *cr){
 	linphone_sql_request(lc->db,buf);
 	sqlite3_free(buf);
 	ms_free(peer);
+	
+	if(cr->unread_count > 0) cr->unread_count = 0;
 }
 
 MSList *linphone_chat_room_get_history_range(LinphoneChatRoom *cr, int startm, int endm){
diff --git a/coreapi/private.h b/coreapi/private.h
index 5366b9699..b48111c67 100644
--- a/coreapi/private.h
+++ b/coreapi/private.h
@@ -556,6 +556,7 @@ struct _LinphoneChatRoom{
 	LinphoneAddress *peer_url;
 	MSList *messages_hist;
 	MSList *transient_messages;
+	int unread_count;
 	LinphoneIsComposingState remote_is_composing;
 	LinphoneIsComposingState is_composing;
 	belle_sip_source_t *remote_composing_refresh_timer;