diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 325ff880e..776c40d98 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -75,6 +75,8 @@ macro(add_unit_test)
         add_test(${_test_NAME} ${_test_LAUNCHER} ${_test_NAME})
     endif(KDE4_TEST_OUTPUT STREQUAL "xml")
 
+    set_tests_properties(${_test_NAME} PROPERTIES ENVIRONMENT "LANG=en_US.UTF-8")
+
     if(NOT MSVC_IDE)   #not needed for the ide
         # if the tests are EXCLUDE_FROM_ALL, add a target "buildtests" to build all tests
         if(NOT WITH_TESTS)