diff --git a/lib/std/process/Child.zig b/lib/std/process/Child.zig
index a31afdc66d..0599763c67 100644
--- a/lib/std/process/Child.zig
+++ b/lib/std/process/Child.zig
@@ -654,7 +654,6 @@ fn spawnPosix(self: *ChildProcess) SpawnError!void {
         setUpChildIo(self.stdin_behavior, stdin_pipe[0], posix.STDIN_FILENO, dev_null_fd) catch |err| forkChildErrReport(err_pipe[1], err);
         setUpChildIo(self.stdout_behavior, stdout_pipe[1], posix.STDOUT_FILENO, dev_null_fd) catch |err| forkChildErrReport(err_pipe[1], err);
         setUpChildIo(self.stderr_behavior, stderr_pipe[1], posix.STDERR_FILENO, dev_null_fd) catch |err| forkChildErrReport(err_pipe[1], err);
-        if (prog_pipe[1] != -1) posix.dup2(prog_pipe[1], prog_fileno) catch |err| forkChildErrReport(err_pipe[1], err);
 
         if (self.cwd_dir) |cwd| {
             posix.fchdir(cwd.fd) catch |err| forkChildErrReport(err_pipe[1], err);
@@ -662,6 +661,10 @@ fn spawnPosix(self: *ChildProcess) SpawnError!void {
             posix.chdir(cwd) catch |err| forkChildErrReport(err_pipe[1], err);
         }
 
+        // Must happen after fchdir above, the cwd file descriptor might be
+        // equal to prog_fileno and be clobbered by this dup2 call.
+        if (prog_pipe[1] != -1) posix.dup2(prog_pipe[1], prog_fileno) catch |err| forkChildErrReport(err_pipe[1], err);
+
         if (self.gid) |gid| {
             posix.setregid(gid, gid) catch |err| forkChildErrReport(err_pipe[1], err);
         }