--- IO-AIO/AIO.xs	2016/07/18 07:48:01	1.243
+++ IO-AIO/AIO.xs	2017/05/30 22:45:52	1.244
@@ -1607,7 +1607,7 @@
 }
 
 void
-aio_mtouch (SV8 *data, IV offset = 0, SV *length = &PL_sv_undef, int flags = 0, SV *callback = &PL_sv_undef)
+aio_mtouch (SV8 *data, IV offset = 0, SV *length = &PL_sv_undef, int flags = -1, SV *callback = &PL_sv_undef)
         ALIAS:
            aio_mtouch = EIO_MTOUCH
            aio_msync  = EIO_MSYNC
@@ -1617,6 +1617,9 @@
         char *svptr = SvPVbyte (data, svlen);
         UV len = SvUV (length);
 
+        if (flags < 0)
+          flags = ix == EIO_MSYNC ? EIO_MS_SYNC : 0;
+
         if (offset < 0)
           offset += svlen;