diff --git a/doc/CHANGES.md b/doc/CHANGES.md
index c5f5f6e..47b5a2f 100644
--- a/doc/CHANGES.md
+++ b/doc/CHANGES.md
@@ -1,6 +1,10 @@
 Change history
 ==============
 
+## v2.9c (2024/xx/xx)
+
+  * Re-sync with `expl3` for deprecated commands.
+
 ## v2.9b (2024/04/27)
 
   * Add new `Letters=Uppercase` (LuaLaTeX only) as an interface to `luaotfload`
diff --git a/fontspec-code-opening.dtx b/fontspec-code-opening.dtx
index 84d4cf6..7c19c34 100644
--- a/fontspec-code-opening.dtx
+++ b/fontspec-code-opening.dtx
@@ -163,7 +163,7 @@
 %
 %    \begin{macrocode}
 \cs_generate_variant:Nn \int_set:Nn {Nv}
-\cs_generate_variant:Nn \prop_gput_if_new:Nnn  {NeV}
+\cs_generate_variant:Nn \prop_gput_if_not_in:Nnn {NeV}
 \cs_generate_variant:Nn \prop_gput:Nnn  {Nxn} % needed by unicode-math
 \cs_generate_variant:Nn \tl_if_empty:nF {f}
 \cs_generate_variant:Nn \tl_if_eq:nnT {oe}
diff --git a/fontspec-code-xfss.dtx b/fontspec-code-xfss.dtx
index a2e330a..6d811ff 100644
--- a/fontspec-code-xfss.dtx
+++ b/fontspec-code-xfss.dtx
@@ -102,8 +102,8 @@
       \clist_map_inline:nn {\strongreset,#1}
         {
           ##1
-          \prop_gput_if_new:NeV \g_@@_strong_prop { \f@series } { \l_@@_strongdef_int }
-          \prop_gput:Nen \g_@@_strong_prop { switch-\int_use:N \l_@@_strongdef_int } { ##1 }
+          \prop_gput_if_not_in:NeV \g_@@_strong_prop { \f@series } { \l_@@_strongdef_int }
+          \prop_gput:Nxn \g_@@_strong_prop { switch-\int_use:N \l_@@_strongdef_int } { ##1 }
           \int_incr:N \l_@@_strongdef_int
         }
     \group_end: