--- libtiff/tiffiop.h
+++ libtiff/tiffiop.h
@@ -184,7 +184,7 @@
 #define	TIFFWriteFile(tif, buf, size) \
 	((*(tif)->tif_writeproc)((tif)->tif_clientdata,buf,size))
 #define	TIFFSeekFile(tif, off, whence) \
-	((*(tif)->tif_seekproc)((tif)->tif_clientdata,(toff_t)(off),whence))
+	((tif)->tif_seekproc?((*(tif)->tif_seekproc)((tif)->tif_clientdata,(toff_t)(off),whence)):0)
 #define	TIFFCloseFile(tif) \
 	((*(tif)->tif_closeproc)((tif)->tif_clientdata))
 #define	TIFFGetFileSize(tif) \