diff --git a/sdk/include/reactos/wine/test.h b/sdk/include/reactos/wine/test.h
index 8b9035adfcf..db723249c5e 100644
--- a/sdk/include/reactos/wine/test.h
+++ b/sdk/include/reactos/wine/test.h
@@ -26,6 +26,11 @@
 #include <windef.h>
 #include <winbase.h>
 
+#ifndef _STRSAFE_H_INCLUDED_
+#include <tchar.h>
+#include <strsafe.h>
+#endif
+
 #ifdef __WINE_CONFIG_H
 #error config.h should not be used in Wine tests
 #endif
@@ -638,14 +643,17 @@ const char *wine_dbgstr_wn( const WCHAR *str, intptr_t n )
 {
     char *dst, *res;
     size_t size;
+    size_t CbLength = 0;
+    HRESULT hr;
 
+    if (!str) return "(null)";
     if (!((ULONG_PTR)str >> 16))
     {
-        if (!str) return "(null)";
         res = get_temp_buffer( 6 );
         sprintf( res, "#%04x", LOWORD(str) );
         return res;
     }
+    if (IsBadStringPtrW(str,n)) return "(invalid)";
     if (n == -1)
     {
         const WCHAR *end = str;
@@ -655,6 +663,17 @@ const char *wine_dbgstr_wn( const WCHAR *str, intptr_t n )
     if (n < 0) n = 0;
     size = 12 + min( 300, n * 5 );
     dst = res = get_temp_buffer( size );
+
+    hr = StringCbLengthW((STRSAFE_LPCWSTR)str, size, &CbLength);
+    if (SUCCEEDED(hr))
+    {
+        n = min(n, CbLength/2);
+    }
+    else
+    {
+        return "(invalid)";
+    }
+
     *dst++ = 'L';
     *dst++ = '"';
     while (n-- > 0 && dst <= res + size - 10)