diff --git a/src/mod_vcard.erl b/src/mod_vcard.erl
index 1820f64b8..46830b020 100644
--- a/src/mod_vcard.erl
+++ b/src/mod_vcard.erl
@@ -219,17 +219,17 @@ set_vcard(User, LServer, VCARD) ->
 	    end,
 
     LUser     = jlib:nodeprep(User),
-    LFN       = string:to_lower(FN),
-    LFamily   = string:to_lower(Family),
-    LGiven    = string:to_lower(Given),
-    LMiddle   = string:to_lower(Middle),
-    LNickname = string:to_lower(Nickname),
-    LBDay     = string:to_lower(BDay),
-    LCTRY     = string:to_lower(CTRY),
-    LLocality = string:to_lower(Locality),
-    LEMail    = string:to_lower(EMail),
-    LOrgName  = string:to_lower(OrgName),
-    LOrgUnit  = string:to_lower(OrgUnit),
+    LFN       = string2lower(FN),
+    LFamily   = string2lower(Family),
+    LGiven    = string2lower(Given),
+    LMiddle   = string2lower(Middle),
+    LNickname = string2lower(Nickname),
+    LBDay     = string2lower(BDay),
+    LCTRY     = string2lower(CTRY),
+    LLocality = string2lower(Locality),
+    LEMail    = string2lower(EMail),
+    LOrgName  = string2lower(OrgName),
+    LOrgUnit  = string2lower(OrgUnit),
 
     US = {LUser, LServer},
 
@@ -271,6 +271,12 @@ set_vcard(User, LServer, VCARD) ->
 	    ejabberd_hooks:run(vcard_set, LServer, [LUser, LServer, VCARD])
     end.
 
+string2lower(String) ->
+    case stringprep:tolower(String) of
+        Lower when is_list(Lower) -> Lower;
+        error -> string:to_lower(String)
+    end.
+
 -define(TLFIELD(Type, Label, Var),
 	{xmlelement, "field", [{"type", Type},
 			       {"label", translate:translate(Lang, Label)},
@@ -541,7 +547,7 @@ filter_fields([], Match, _LServer) ->
     Match;
 filter_fields([{SVar, [Val]} | Ds], Match, LServer)
   when is_list(Val) and (Val /= "") ->
-    LVal = string:to_lower(Val),
+    LVal = string2lower(Val),
     NewMatch = case SVar of
                    "user" ->
 		       case gen_mod:get_module_opt(LServer, ?MODULE,
@@ -618,17 +624,17 @@ set_vcard_t(R, _) ->
     OrgUnit  = xml:get_path_s(VCARD, [{elem, "ORG"}, {elem, "ORGUNIT"}, cdata]),
 
     {LUser, _LServer} = US,
-    LFN       = string:to_lower(FN),
-    LFamily   = string:to_lower(Family),
-    LGiven    = string:to_lower(Given),
-    LMiddle   = string:to_lower(Middle),
-    LNickname = string:to_lower(Nickname),
-    LBDay     = string:to_lower(BDay),
-    LCTRY     = string:to_lower(CTRY),
-    LLocality = string:to_lower(Locality),
-    LEMail    = string:to_lower(EMail),
-    LOrgName  = string:to_lower(OrgName),
-    LOrgUnit  = string:to_lower(OrgUnit),
+    LFN       = string2lower(FN),
+    LFamily   = string2lower(Family),
+    LGiven    = string2lower(Given),
+    LMiddle   = string2lower(Middle),
+    LNickname = string2lower(Nickname),
+    LBDay     = string2lower(BDay),
+    LCTRY     = string2lower(CTRY),
+    LLocality = string2lower(Locality),
+    LEMail    = string2lower(EMail),
+    LOrgName  = string2lower(OrgName),
+    LOrgUnit  = string2lower(OrgUnit),
 
     if
 	(LUser     == error) or
diff --git a/src/mod_vcard_odbc.erl b/src/mod_vcard_odbc.erl
index a4c23624c..fd1ca9022 100644
--- a/src/mod_vcard_odbc.erl
+++ b/src/mod_vcard_odbc.erl
@@ -186,17 +186,17 @@ set_vcard(User, LServer, VCARD) ->
 	    end,
 
     LUser     = jlib:nodeprep(User),
-    LFN       = string:to_lower(FN),
-    LFamily   = string:to_lower(Family),
-    LGiven    = string:to_lower(Given),
-    LMiddle   = string:to_lower(Middle),
-    LNickname = string:to_lower(Nickname),
-    LBDay     = string:to_lower(BDay),
-    LCTRY     = string:to_lower(CTRY),
-    LLocality = string:to_lower(Locality),
-    LEMail    = string:to_lower(EMail),
-    LOrgName  = string:to_lower(OrgName),
-    LOrgUnit  = string:to_lower(OrgUnit),
+    LFN       = string2lower(FN),
+    LFamily   = string2lower(Family),
+    LGiven    = string2lower(Given),
+    LMiddle   = string2lower(Middle),
+    LNickname = string2lower(Nickname),
+    LBDay     = string2lower(BDay),
+    LCTRY     = string2lower(CTRY),
+    LLocality = string2lower(Locality),
+    LEMail    = string2lower(EMail),
+    LOrgName  = string2lower(OrgName),
+    LOrgUnit  = string2lower(OrgUnit),
 
     if
 	(LUser     == error) or
@@ -252,6 +252,12 @@ set_vcard(User, LServer, VCARD) ->
 	    ejabberd_hooks:run(vcard_set, LServer, [LUser, LServer, VCARD])
     end.
 
+string2lower(String) ->
+    case stringprep:tolower(String) of
+	Lower when is_list(Lower) -> Lower;
+	error -> string:to_lower(String)
+    end.
+
 -define(TLFIELD(Type, Label, Var),
 	{xmlelement, "field", [{"type", Type},
 			       {"label", translate:translate(Lang, Label)},
@@ -531,7 +537,7 @@ filter_fields([], Match, _LServer) ->
     end;
 filter_fields([{SVar, [Val]} | Ds], Match, LServer)
   when is_list(Val) and (Val /= "") ->
-    LVal = string:to_lower(Val),
+    LVal = string2lower(Val),
     NewMatch = case SVar of
                    "user"     -> make_val(Match, "lusername", LVal);
                    "fn"       -> make_val(Match, "lfn",       LVal);