diff --git a/src/fileio.c b/src/fileio.c
index dfab3de..69aa3f6 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -1929,7 +1929,7 @@ permissions.  */)
     }
 #else /* not WINDOWSNT */
   immediate_quit = 1;
-  ifd = emacs_open (SSDATA (encoded_file), O_RDONLY, 0);
+  ifd = emacs_open (SSDATA (encoded_file), O_RDONLY | O_BINARY, 0);
   immediate_quit = 0;
 
   if (ifd < 0)
@@ -1963,15 +1963,15 @@ permissions.  */)
   new_mask = S_IREAD | S_IWRITE;
 #endif
 
-  ofd = emacs_open (SSDATA (encoded_newname), O_WRONLY | O_CREAT | O_EXCL,
-		    new_mask);
+  ofd = emacs_open (SSDATA (encoded_newname),
+		    O_WRONLY | O_CREAT | O_EXCL | O_BINARY, new_mask);
   if (ofd < 0 && errno == EEXIST)
     {
       if (NILP (ok_if_already_exists) || INTEGERP (ok_if_already_exists))
 	barf_or_query_if_file_exists (newname, true, "copy to it",
 				      INTEGERP (ok_if_already_exists), false);
       already_exists = true;
-      ofd = emacs_open (SSDATA (encoded_newname), O_WRONLY, 0);
+      ofd = emacs_open (SSDATA (encoded_newname), O_WRONLY | O_BINARY, 0);
     }
   if (ofd < 0)
     report_file_error ("Opening output file", newname);