diff --git a/setup/installer/windows/freeze.py b/setup/installer/windows/freeze.py
index 026cac99cf..343a8978cb 100644
--- a/setup/installer/windows/freeze.py
+++ b/setup/installer/windows/freeze.py
@@ -373,7 +373,7 @@ class Win32Freeze(Command, WixMixIn):
         src = self.j(self.src_root, 'setup', 'installer', 'windows',
                 'portable.c')
         obj = self.j(self.obj_dir, self.b(src)+'.obj')
-        cflags  = '/c /EHsc /MT /W3 /Ox /nologo /D_UNICODE'.split()
+        cflags  = '/c /EHsc /MT /W3 /Ox /nologo /D_UNICODE /DUNICODE'.split()
 
         if self.newer(obj, [src]):
             self.info('Compiling', obj)
diff --git a/setup/installer/windows/portable.c b/setup/installer/windows/portable.c
index 05763bc303..1a2a89df7b 100644
--- a/setup/installer/windows/portable.c
+++ b/setup/installer/windows/portable.c
@@ -2,8 +2,14 @@
 #define UNICODE
 #endif 
 
+#ifndef _UNICODE
+#define _UNICODE
+#endif 
+
+
 #include <windows.h>
 #include <tchar.h>
+#include <wchar.h>
 #include <stdio.h>
 
 #define BUFSIZE 4096
@@ -32,7 +38,7 @@ void show_last_error_crt(LPCTSTR preamble) {
     int err = 0;
 
     _get_errno(&err);
-    _wcserror_s(buf, BUFSIZE, err);
+    _tcserror_s(buf, BUFSIZE, err);
     show_detailed_error(preamble, buf, err);
 }
 
diff --git a/src/calibre/ebooks/mobi/writer2/main.py b/src/calibre/ebooks/mobi/writer2/main.py
index 4d53b7c3ef..2c57a9e461 100644
--- a/src/calibre/ebooks/mobi/writer2/main.py
+++ b/src/calibre/ebooks/mobi/writer2/main.py
@@ -544,7 +544,8 @@ class MobiWriter(object):
         '''
         Write the PalmDB header
         '''
-        title = ascii_filename(unicode(self.oeb.metadata.title[0]))
+        title = ascii_filename(unicode(self.oeb.metadata.title[0])).replace(
+                ' ', '_')
         title = title + (b'\0' * (32 - len(title)))
         now = int(time.time())
         nrecords = len(self.records)