diff --git a/kernel/src/sys/stdio.cpp b/kernel/src/sys/stdio.cpp
index a32e8d55..9ad01b8f 100644
--- a/kernel/src/sys/stdio.cpp
+++ b/kernel/src/sys/stdio.cpp
@@ -20,7 +20,7 @@
 
 #define FNCTL_DUPFD 0
 
-void sys_fcntl(Context* context, int fd, int command, [[maybe_unused]] uintptr_t arg)
+void sys_fcntl(Context* context, int fd, int command, uintptr_t arg)
 {
     if (fd >= TASK_MAX_FDS || fd < 0)
     {
@@ -34,10 +34,14 @@ void sys_fcntl(Context* context, int fd, int command, [[maybe_unused]] uintptr_t
         return;
     }
     Descriptor& file = current_task->files[fd];
-    if (command == FNCTL_DUPFD) // FIXME: If arg is greater than 0, return the lowest numbered available file descriptor
-                                // greater than or equal to arg.
+    if (command == FNCTL_DUPFD)
     {
-        int dupfd = current_task->alloc_fd();
+        if ((int)arg < 0 || (int)arg >= TASK_MAX_FDS)
+        {
+            context->rax = -EINVAL;
+            return;
+        }
+        int dupfd = current_task->alloc_fd_greater_than_or_equal((int)arg);
         if (dupfd < 0)
         {
             context->rax = -EMFILE;