Index: lib/rtl/nls.c
===================================================================
--- lib/rtl/nls.c	(revision 41188)
+++ lib/rtl/nls.c	(working copy)
@@ -33,6 +33,10 @@
 PWCHAR NlsDbcsUnicodeToOemTable = NULL;
 PUSHORT _NlsOemLeadByteInfo = NULL; /* exported */
 
+USHORT NlsOemDefaultChar = '\0'; /* exported */
+USHORT NlsUnicodeDefaultChar = 0; /* exported */
+
+
 #define NlsOemLeadByteInfo              _NlsOemLeadByteInfo
 #define INIT_FUNCTION
 
@@ -435,6 +439,10 @@
    /* Set Unicode case map data */
    NlsUnicodeUpcaseTable = NlsTable->UpperCaseTable;
    NlsUnicodeLowercaseTable = NlsTable->LowerCaseTable;
+
+   /* set the default characters for RtlpDidUnicodeToOemWork */
+   NlsOemDefaultChar = NlsTable->OemTableInfo.DefaultChar;
+   NlsUnicodeDefaultChar = NlsTable->OemTableInfo.TransDefaultChar;
 }
 
 
Index: lib/rtl/unicode.c
===================================================================
--- lib/rtl/unicode.c	(revision 41188)
+++ lib/rtl/unicode.c	(working copy)
@@ -23,6 +23,9 @@
 extern BOOLEAN NlsMbOemCodePageTag;
 extern PUSHORT NlsLeadByteInfo;
 
+extern USHORT NlsOemDefaultChar;
+extern USHORT NlsUnicodeDefaultChar;
+
 /* FUNCTIONS *****************************************************************/
 
 /*
@@ -395,7 +398,42 @@
     }
 }
 
+
 /*
+ * @implemented
+ * 
+ * NOTES
+ *  Check the oem-string to match the uincoded-string.
+ *
+ *  Functions who convert unicode strings to oem strings will set a DefaultChar from 
+ *  the OemCodepage when the character are unknown. So check it against the unicode string
+ *  and return false when the unicode string not contain an TransDefaultChar.
+ */
+BOOLEAN
+NTAPI
+RtlpDidUnicodeToOemWork(IN PUNICODE_STRING  UnicodeString,IN POEM_STRING OemString)
+{
+   ULONG i;
+
+   if ((OemString != NULL) && (OemString->Buffer != NULL))
+   {
+      i = 0;
+      while ((OemString->Buffer[i]!=0) && (i<OemString->Length))
+      {
+         if ((OemString->Buffer[i]==NlsOemDefaultChar) && 
+             (UnicodeString->Buffer[i]!=NlsUnicodeDefaultChar))
+         {
+            return FALSE;
+         }
+         i++;
+      }
+      return TRUE;
+   }
+
+   return FALSE;
+}
+
+/*
 * @unimplemented
 */
 BOOLEAN
@@ -1534,8 +1572,14 @@
                               UniSource->Buffer,
                               UniSource->Length);
 
-    /* FIXME: Check if everything mapped correctly and
-     * return STATUS_UNMAPPABLE_CHARACTER */
+    if (NT_SUCCESS(Status))
+    {
+       /* check for unmapped character */
+       if (RtlpDidUnicodeToOemWork(UniSource,OemDest) == FALSE)
+       {
+          Status = STATUS_UNMAPPABLE_CHARACTER;
+       }
+    }
 
     if (!NT_SUCCESS(Status) && AllocateDestinationString)
     {
@@ -1763,7 +1807,14 @@
                                     UniSource->Buffer,
                                     UniSource->Length);
 
-    /* FIXME: Special check needed and return STATUS_UNMAPPABLE_CHARACTER */
+    if (NT_SUCCESS(Status))
+    {
+       /* check for unmapped character */
+       if (RtlpDidUnicodeToOemWork((PUNICODE_STRING)UniSource,OemDest) == FALSE)
+       {
+          Status = STATUS_UNMAPPABLE_CHARACTER;
+       }
+    }
 
     if (!NT_SUCCESS(Status) && AllocateDestinationString)
     {
@@ -1816,7 +1867,14 @@
                                     UniSource->Buffer,
                                     UniSource->Length);
 
-    /* FIXME: Special check needed and return STATUS_UNMAPPABLE_CHARACTER */
+    if (NT_SUCCESS(Status))
+    {
+       /* check for unmapped character */
+       if (RtlpDidUnicodeToOemWork((PUNICODE_STRING)UniSource,OemDest) == FALSE)
+       {
+          Status = STATUS_UNMAPPABLE_CHARACTER;
+       }
+    }
 
     if (!NT_SUCCESS(Status) && AllocateDestinationString)
     {