diff --git a/src/helpers.cpp b/src/helpers.cpp
index 020e8119a..47531e8af 100644
--- a/src/helpers.cpp
+++ b/src/helpers.cpp
@@ -678,6 +678,41 @@ std::string Helpers::toUpper(std::string const & s) {
     return lc;
 }
 
+// capitalizes one UTF-8 character in char array
+// works with Latin1 (1 byte) and Polish (2 bytes) characters
+// TODO add special characters that occur in other supported languages
+void Helpers::CharToUpperUTF8(char * c) {
+    switch (*c) {
+    case 0xC3:
+        if (*(c + 1) == 0xB3) //ó (0xC3,0xB3) -> Ó (0xC3,0x93)
+            *(c + 1) = 0x93;
+        break;
+    case 0xC4:
+        switch (*(c + 1)) {
+        case 0x85: //ą (0xC4,0x85) -> Ą (0xC4,0x84)
+        case 0x87: //ć (0xC4,0x87) -> Ć (0xC4,0x86)
+        case 0x99: //ę (0xC4,0x99) -> Ę (0xC4,0x98)
+            *(c + 1) = *(c + 1) - 1;
+            break;
+        }
+        break;
+    case 0xC5:
+        switch (*(c + 1)) {
+        case 0x82: //ł (0xC5,0x82) -> Ł (0xC5,0x81)
+        case 0x84: //ń (0xC5,0x84) -> Ń (0xC5,0x83)
+        case 0x9B: //ś (0xC5,0x9B) -> Ś (0xC5,0x9A)
+        case 0xBA: //ź (0xC5,0xBA) -> Ź (0xC5,0xB9)
+        case 0xBC: //ż (0xC5,0xBC) -> Ż (0xC5,0xBB)
+            *(c + 1) = *(c + 1) - 1;
+            break;
+        }
+        break;
+    default:
+        *c = toupper(*c); //works on Latin1 letters
+        break;
+    }
+}
+
 // replace char in char string
 void Helpers::replace_char(char * str, char find, char replace) {
     if (str == nullptr) {
diff --git a/src/helpers.h b/src/helpers.h
index e4505643c..67b633227 100644
--- a/src/helpers.h
+++ b/src/helpers.h
@@ -55,6 +55,7 @@ class Helpers {
     static std::string toLower(std::string const & s);
     static std::string toUpper(std::string const & s);
     static std::string toLower(const char * s);
+    static void CharToUpperUTF8(char * c);
 
     static void replace_char(char * str, char find, char replace);
 
diff --git a/src/mqtt.cpp b/src/mqtt.cpp
index 80749352b..d2fe4b174 100644
--- a/src/mqtt.cpp
+++ b/src/mqtt.cpp
@@ -907,7 +907,7 @@ void Mqtt::publish_ha_sensor_config(DeviceValue & dv, const std::string & model,
 
     if (create_device_config) {
         auto cap_name          = strdup(device_type_name);
-        cap_name[0]            = toupper(cap_name[0]); // capitalize
+        Helpers::CharToUpperUTF8(cap_name); // capitalize first letter
         dev_json["name"]       = std::string("EMS-ESP ") + cap_name;
         dev_json["mf"]         = brand;
         dev_json["mdl"]        = model;
@@ -1132,7 +1132,7 @@ void Mqtt::publish_ha_sensor_config(uint8_t               type,        // EMSdev
     // friendly name = <tag> <name>
     char   ha_name[70];
     char * F_name = strdup(fullname);
-    F_name[0]     = toupper(F_name[0]); // capitalize first letter
+    Helpers::CharToUpperUTF8(F_name); // capitalize first letter
     if (EMSdevice::tag_to_string(tag).empty()) {
         snprintf(ha_name, sizeof(ha_name), "%s", F_name); // no tag
     } else {