diff --git a/src/iomux_select.c b/src/iomux_select.c
index 488450b..9f71773 100644
--- a/src/iomux_select.c
+++ b/src/iomux_select.c
@@ -44,7 +44,7 @@ static int iomux_select_update_events(struct IOMux *mux_, struct IOMuxFD *fd)
     struct IOMuxSelect *mux = mux_->instance;
 
     if (fd->fd < 0 || fd->fd >= FD_SETSIZE) {
-        return EINVAL;
+        return ENFILE;
     }
 
     if (fd->what & MUX_EV_READ)
@@ -70,7 +70,7 @@ static int iomux_select_register_fd(struct IOMux *mux_, struct IOMuxFD *fd)
 
     rc = iomux_select_update_events(mux_, fd);
     if (rc != 0) {
-        return ENFILE;
+        return rc;
     }
 
     mux->descriptors[fd->fd] = fd;