--- IO-AIO/AIO.xs	2008/10/22 18:15:36	1.133
+++ IO-AIO/AIO.xs	2009/04/19 13:05:06	1.134
@@ -657,9 +657,13 @@
         STRLEN svlen;
         char *svptr = SvPVbyte (data, svlen);
         UV len = SvUV (length);
+        int fd;
+
+        if (SvTYPE (data) > SVt_PVMG)
+          croak ("illegal data argument '%s', must be plain scalar string", SvPV_nolen (data));
 
         SvUPGRADE (data, SVt_PV);
-        SvPOK_on (data);
+        SvPOK_only (data);
 
         if (dataoffset < 0)
           dataoffset += svlen;
@@ -682,13 +686,18 @@
         if (len < 0)
           croak ("length must not be negative");
 
+        fd = PerlIO_fileno (ix == EIO_READ ? IoIFP (sv_2io (fh))
+                                           : IoOFP (sv_2io (fh)));
+
+        if (fd < 0)
+          croak ("illegal fh argument, either not an OS file or read/write mode mismatch");
+
         {
           dREQ;
 
           req->type = ix;
           req->sv1  = newSVsv (fh);
-          req->int1 = PerlIO_fileno (ix == EIO_READ ? IoIFP (sv_2io (fh))
-                                                    : IoOFP (sv_2io (fh)));
+          req->int1 = df;
           req->offs = SvOK (offset) ? SvVAL64 (offset) : -1;
           req->size = len;
           req->sv2  = SvREFCNT_inc (data);