diff --git a/tex/polyglossia.sty b/tex/polyglossia.sty
index 77dc0e1e..109b6d1c 100644
--- a/tex/polyglossia.sty
+++ b/tex/polyglossia.sty
@@ -226,6 +226,16 @@
 %
 % END MESSAGES
 
+\prg_set_conditional:Nnn \xpg_if_in_preamble: {T, F, TF}
+  {
+    \cs_if_eq:NNTF { \@onlypreamble } { \@notprerr }
+      {
+        \prg_return_false:
+      }{
+        \prg_return_true:
+      }
+  }
+
 %% Used by the language definitions files for right-to-left languages
 \cs_new_nopar:Npn \RequireBidi
 {