diff --git a/tests/strings/strings.cpp b/tests/strings/strings.cpp
index ea4e04fc58..3e25c70f48 100644
--- a/tests/strings/strings.cpp
+++ b/tests/strings/strings.cpp
@@ -459,8 +459,11 @@ void StringTestCase::CaseChanges()
     if ( locRu.IsOk() )
     {
         // try upper casing 8bit strings
-        wxString sUpper("\xdf"),
-                 sLower("\xff");
+        const wchar_t capital_ya[] = { 0x42f, 0 },
+                      small_ya[]   = { 0x44f, 0 };
+
+        wxString sUpper(wxConvLibc.cWC2MB(capital_ya)),
+                 sLower(wxConvLibc.cWC2MB(small_ya));
 
         CPPUNIT_ASSERT( sUpper.Lower() == sLower );
         CPPUNIT_ASSERT( sLower.Upper() == sUpper );