diff --git a/development/scons/SConstruct b/development/scons/SConstruct
index bd13109e53..6d7ea19578 100644
--- a/development/scons/SConstruct
+++ b/development/scons/SConstruct
@@ -1018,6 +1018,7 @@ return std::count(a, a+5, 'l');
         ('std::istreambuf_iterator<std::istream>', 'HAVE_DECL_ISTREAMBUF_ITERATOR',
             '#include <streambuf>\n#include <istream>'),
         ('wchar_t', 'HAVE_WCHAR_T', None),
+        ('mode_t', 'HAVE_MODE_T', "#include <sys/types.h>"),
     ],
     libs = [
         ('gdi32', 'HAVE_LIBGDI32'),
diff --git a/src/support/copy.C b/src/support/copy.C
index ceb2db1968..3b6d328bd7 100644
--- a/src/support/copy.C
+++ b/src/support/copy.C
@@ -33,7 +33,7 @@ using std::string;
 
 bool lyx::support::chmod(string const & file, unsigned long int mode)
 {
-#ifdef HAVE_CHMOD
+#if defined (HAVE_CHMOD) && defined (HAVE_MODE_T)
 	if (::chmod(file.c_str(), mode_t(mode)) != 0)
 		return false;
 #else