diff --git a/include/wx/filefn.h b/include/wx/filefn.h
index ad264b723b..269a645e82 100644
--- a/include/wx/filefn.h
+++ b/include/wx/filefn.h
@@ -202,7 +202,7 @@ enum wxFileKind
     // to avoid using them as they're not present in earlier versions and
     // always using the native functions spelling is easier than testing for
     // the versions
-    #if defined(__BORLANDC__) || defined(__DMC__) || defined(__WATCOMC__)
+    #if defined(__BORLANDC__) || defined(__DMC__) || defined(__WATCOMC__) || defined(__MINGW64__)
         #define wxPOSIX_IDENT(func)    ::func
     #else // by default assume MSVC-compatible names
         #define wxPOSIX_IDENT(func)    _ ## func
@@ -237,9 +237,16 @@ enum wxFileKind
     #endif
 
     #ifdef wxHAS_HUGE_FILES
-        #define   wxSeek       wxPOSIX_IDENT(lseeki64)
-        #define   wxLseek      wxPOSIX_IDENT(lseeki64)
-        #define   wxTell       wxPOSIX_IDENT(telli64)
+        #ifndef __MINGW64__
+            #define   wxSeek       wxPOSIX_IDENT(lseeki64)
+            #define   wxLseek      wxPOSIX_IDENT(lseeki64)
+            #define   wxTell       wxPOSIX_IDENT(telli64)
+        #else
+            // unfortunately, mingw-W64 is somewhat inconsistent...
+            #define   wxSeek       _lseeki64
+            #define   wxLseek      _lseeki64
+            #define   wxTell       _telli64
+        #endif
     #else // !wxHAS_HUGE_FILES
         #define   wxSeek       wxPOSIX_IDENT(lseek)
         #define   wxLseek      wxPOSIX_IDENT(lseek)
diff --git a/include/wx/msw/wrapwin.h b/include/wx/msw/wrapwin.h
index 60aa48e553..f6e1a0f8a4 100644
--- a/include/wx/msw/wrapwin.h
+++ b/include/wx/msw/wrapwin.h
@@ -77,7 +77,7 @@
 // pointer) on MSVC 7 and later. However, they are not available in older 
 // Platform SDKs, and since they are typedefs and not #defines we simply 
 // overwrite them if there is a chance that they're not defined
-#if !defined(_MSC_VER) || (_MSC_VER < 1300)
+#if (!defined(_MSC_VER) || (_MSC_VER < 1300)) && !defined(__WIN64__)
     #define UINT_PTR unsigned int
     #define INT_PTR int
     #define LONG_PTR long
diff --git a/include/wx/platform.h b/include/wx/platform.h
index 8f6545c3f4..4db7828771 100644
--- a/include/wx/platform.h
+++ b/include/wx/platform.h
@@ -505,7 +505,7 @@
 
     /* size_t is the same as unsigned int for all Windows compilers we know, */
     /* so define it if it hadn't been done by configure yet */
-#    if !defined(wxSIZE_T_IS_UINT) && !defined(wxSIZE_T_IS_ULONG)
+#    if !defined(wxSIZE_T_IS_UINT) && !defined(wxSIZE_T_IS_ULONG) && !defined(__WIN64__)
 #        define wxSIZE_T_IS_UINT
 #    endif
 #endif  /* OS */