--- a/util/jsonschema.lua	Sun Apr 23 10:26:43 2023 +0200
+++ b/util/jsonschema.lua	Sun Apr 23 10:42:07 2023 +0200
@@ -3,6 +3,12 @@
 local m_type = function(n)
 	return type(n) == "number" and n % 1 == 0 and n <= 9007199254740992 and n >= -9007199254740992 and "integer" or "float";
 end;
+
+local utf8 = rawget(_G, "utf8") or require("prosody.util.encodings").utf8;
+local utf8_len = utf8.len or function(s)
+	local _, count = s:gsub("[%z\001-\127\194-\253][\128-\191]*", "");
+	return count
+end;
 local json = require("prosody.util.json")
 local null = json.null;
 
@@ -103,10 +109,10 @@
 	end
 
 	if type(data) == "string" then
-		if schema.maxLength and #data > schema.maxLength then
+		if schema.maxLength and utf8_len(data) > schema.maxLength then
 			return false
 		end
-		if schema.minLength and #data < schema.minLength then
+		if schema.minLength and utf8_len(data) < schema.minLength then
 			return false
 		end
 		if schema.luaPattern and not data:match(schema.luaPattern) then