diff --git a/src/kauthactionreply.h b/src/kauthactionreply.h
--- a/src/kauthactionreply.h
+++ b/src/kauthactionreply.h
@@ -191,6 +191,9 @@
  kauth_install_helper_files(<helper_target> <helper_id> <user>)
  @endcode
 
+ As locale is not inherited, the auth helper will have the text codec explicitly set
+ to use UTF-8 on unix machines.
+
  The first argument is the cmake target name for the helper executable, which
  you have to build and install separately. Make sure to INSTALL THE HELPER IN
  ${KAUTH_HELPER_INSTALL_DIR}, otherwise kauth_install_helper_files will not work. The
diff --git a/src/kauthhelpersupport.cpp b/src/kauthhelpersupport.cpp
--- a/src/kauthhelpersupport.cpp
+++ b/src/kauthhelpersupport.cpp
@@ -43,6 +43,9 @@
 
 #include <QCoreApplication>
 #include <QTimer>
+#ifdef Q_OS_UNIX
+#include <QTextCodec>
+#endif
 
 #include "BackendsManager.h"
 
@@ -76,6 +79,11 @@
 {
 #ifdef Q_OS_UNIX
     fixEnvironment();
+    //As we don't inherit lang, the locale could be something that doesn't support UTF-8. Force it
+    auto utf8Codec = QTextCodec::codecForName("UTF-8");
+    if (utf8Codec) {
+        QTextCodec::setCodecForLocale(utf8Codec);
+    }
 #endif
 
 #ifdef Q_OS_OSX