diff --git a/exec.cpp b/exec.cpp
index e72a787f5..2aa13dc1b 100644
--- a/exec.cpp
+++ b/exec.cpp
@@ -406,11 +406,6 @@ static bool io_transmogrify(const io_chain_t &in_chain, io_chain_t &out_chain, s
             */
             case IO_FILE:
             {
-                out.reset(new io_data_t());
-                out->fd = in->fd;
-                out->io_mode = IO_FD;
-                out->param2.close_old = 1;
-
                 int fd;
                 if ((fd=open(in->filename_cstr, in->param2.flags, OPEN_MASK))==-1)
                 {
@@ -424,7 +419,7 @@ static bool io_transmogrify(const io_chain_t &in_chain, io_chain_t &out_chain, s
                 }
 
                 opened_fds.push_back(fd);
-                out->param1.old_fd = fd;
+                out.reset(new io_fd_t(in->fd, fd, true));
 
                 break;
             }
@@ -852,7 +847,8 @@ void exec(parser_t &parser, job_t *j)
 
                             case IO_FD:
                             {
-                                builtin_stdin = in->param1.old_fd;
+                                CAST_INIT(const io_fd_t *, in_fd, in.get());
+                                builtin_stdin = in_fd->old_fd;
                                 break;
                             }
                             case IO_PIPE:
diff --git a/io.cpp b/io.cpp
index 33045bcf4..8bbc07438 100644
--- a/io.cpp
+++ b/io.cpp
@@ -61,9 +61,6 @@ void io_data_t::print() const
         case IO_PIPE:
             fprintf(stderr, "pipe {%d, %d}\n", param1.pipe_fd[0], param1.pipe_fd[1]);
             break;
-        case IO_FD:
-            fprintf(stderr, "FD map %d -> %d\n", param1.old_fd, fd);
-            break;
         case IO_BUFFER:
             fprintf(stderr, "buffer %p (size %lu)\n", out_buffer_ptr(), out_buffer_size());
             break;
@@ -75,6 +72,11 @@ void io_close_t::print() const
     fprintf(stderr, "close %d\n", fd);
 }
 
+void io_fd_t::print() const
+{
+    fprintf(stderr, "FD map %d -> %d\n", old_fd, fd);
+}
+
 void io_buffer_read(io_data_t *d)
 {
     exec_close(d->param1.pipe_fd[1]);
diff --git a/io.h b/io.h
index d7ddbd0ec..627bfc39c 100644
--- a/io.h
+++ b/io.h
@@ -37,8 +37,6 @@ public:
     {
         /** Fds for IO_PIPE and for IO_BUFFER */
         int pipe_fd[2];
-        /** fd to redirect specified fd to, for IO_FD */
-        int old_fd;
     } param1;
 
 
@@ -47,8 +45,6 @@ public:
     {
         /** file creation flags to send to open for IO_FILE */
         int flags;
-        /** Whether to close old_fd for IO_FD */
-        int close_old;
     } param2;
 
     /** Filename IO_FILE. malloc'd. This needs to be used after fork, so don't use wcstring here. */
@@ -127,6 +123,24 @@ public:
     virtual void print() const;
 };
 
+class io_fd_t : public io_data_t
+{
+public:
+    /** fd to redirect specified fd to */
+    int old_fd;
+    /** Whether to close old_fd */
+    int close_old;
+
+    virtual void print() const;
+
+    io_fd_t(int f, int old, bool close = false) :
+        io_data_t(IO_FD, f),
+        old_fd(old),
+        close_old(close)
+    {
+    }
+};
+
 class io_chain_t : public std::vector<shared_ptr<io_data_t> >
 {
 public:
diff --git a/parser.cpp b/parser.cpp
index 1c5f330b2..1329cea62 100644
--- a/parser.cpp
+++ b/parser.cpp
@@ -1607,13 +1607,11 @@ void parser_t::parse_job_argument_list(process_t *p,
                                 {
                                     wchar_t *end;
 
-                                    new_io.reset(new io_data_t(IO_FD, fd));
                                     errno = 0;
 
-                                    new_io->param1.old_fd = fish_wcstoi(target.c_str(), &end, 10);
+                                    int old_fd = fish_wcstoi(target.c_str(), &end, 10);
 
-                                    if ((new_io->param1.old_fd < 0) ||
-                                            errno || *end)
+                                    if (old_fd < 0 || errno || *end)
                                     {
                                         error(SYNTAX_ERROR,
                                               tok_get_pos(tok),
@@ -1622,6 +1620,10 @@ void parser_t::parse_job_argument_list(process_t *p,
 
                                         tok_next(tok);
                                     }
+                                    else
+                                    {
+                                        new_io.reset(new io_fd_t(fd, old_fd));
+                                    }
                                 }
                                 break;
                             }
diff --git a/postfork.cpp b/postfork.cpp
index 9b8913cec..a5602ad19 100644
--- a/postfork.cpp
+++ b/postfork.cpp
@@ -169,7 +169,7 @@ static int handle_child_io(io_chain_t &io_chain)
         io_data_t *io = io_chain.at(idx).get();
         int tmp;
 
-        if (io->io_mode == IO_FD && io->fd == io->param1.old_fd)
+        if (io->io_mode == IO_FD && io->fd == static_cast<io_fd_t*>(io)->old_fd)
         {
             continue;
         }
@@ -232,7 +232,7 @@ static int handle_child_io(io_chain_t &io_chain)
                 */
                 close(io->fd);
 
-                if (dup2(io->param1.old_fd, io->fd) == -1)
+                if (dup2(static_cast<const io_fd_t *>(io)->old_fd, io->fd) == -1)
                 {
                     debug_safe_int(1, FD_ERROR, io->fd);
                     safe_perror("dup2");
@@ -443,9 +443,11 @@ bool fork_actions_make_spawn_properties(posix_spawnattr_t *attr, posix_spawn_fil
     {
         shared_ptr<const io_data_t> io = j->io.at(idx);
 
-        if (io->io_mode == IO_FD && io->fd == io->param1.old_fd)
+        if (io->io_mode == IO_FD)
         {
-            continue;
+            CAST_INIT(const io_fd_t *, io_fd, io.get());
+            if (io->fd == io_fd->old_fd)
+                continue;
         }
 
         if (io->fd > 2)
@@ -472,8 +474,9 @@ bool fork_actions_make_spawn_properties(posix_spawnattr_t *attr, posix_spawn_fil
 
             case IO_FD:
             {
+                CAST_INIT(const io_fd_t *, io_fd, io.get());
                 if (! err)
-                    err = posix_spawn_file_actions_adddup2(actions, io->param1.old_fd /* from */, io->fd /* to */);
+                    err = posix_spawn_file_actions_adddup2(actions, io_fd->old_fd /* from */, io->fd /* to */);
                 break;
             }