diff --git a/include/wx/longlong.h b/include/wx/longlong.h
index d2f1ed26de..5ff8a9b01c 100644
--- a/include/wx/longlong.h
+++ b/include/wx/longlong.h
@@ -27,8 +27,10 @@
 
 // define this to compile wxLongLongWx in "test" mode: the results of all
 // calculations will be compared with the real results taken from
-// wxLongLongNative
-#define wxLONGLONG_TEST_MODE
+// wxLongLongNative -- this is extremely useful to find the bugs in
+// wxLongLongWx class!
+
+//#define wxLONGLONG_TEST_MODE
 
 #ifdef wxLONGLONG_TEST_MODE
     #define wxUSE_LONGLONG_WX 1
diff --git a/src/common/longlong.cpp b/src/common/longlong.cpp
index 6a0cc8e315..5fd1016b5f 100644
--- a/src/common/longlong.cpp
+++ b/src/common/longlong.cpp
@@ -91,34 +91,26 @@ wxLongLongWx& wxLongLongWx::Assign(double d)
 {
     bool positive = d >= 0;
     d = fabs(d);
-    if ( d <= LONG_MAX )
+    if ( d <= ULONG_MAX )
     {
         m_hi = 0;
         m_lo = (long)d;
     }
     else
     {
-#if 0
-        m_lo = (long)d;
-        d -= m_lo;
-        d /=  0x1000;
-        d /=  0x1000;
-        d /=  0x100;
-        m_hi = (long)d;
-#else
-        wxFAIL_MSG(_T("TODO"));
-#endif
+        m_hi = (unsigned long)(d / (1.0 + (double)ULONG_MAX));
+        m_lo = (unsigned long)(d - ((double)m_hi * (1.0 + (double)ULONG_MAX)));
     }
 
-    if ( !positive )
-        m_hi = -m_hi;
-
 #ifdef wxLONGLONG_TEST_MODE
     m_ll = (wxLongLong_t)d;
 
     Check();
 #endif // wxLONGLONG_TEST_MODE
 
+    if ( !positive )
+        Negate();
+
     return *this;
 }