commit 50f8f706e868f8ebac4f2f1392365f994d674463 (HEAD, origin/upgrade-ppxlib-0.18.0)
Author: Nathan Rebours <nathan.p.rebours@gmail.com>
Date:   Mon Oct 5 17:56:52 2020 +0200

    Make ppx_custom_printf compatible with ppxlib.0.18.0
    
    ppxlib.0.18.0 upgrades to the 4.11 AST which results in a change
    in string constants representation. This PR makes ppx_custom_printf
    compatible with the latest ppxlib.
    
    You might want for the actual release of ppxlib.0.18.0 before merging
    this!
    
    Signed-off-by: Nathan Rebours <nathan.p.rebours@gmail.com>

diff --git a/ppx_custom_printf.opam b/ppx_custom_printf.opam
index 80ea710..1cc3d11 100644
--- a/ppx_custom_printf.opam
+++ b/ppx_custom_printf.opam
@@ -15,7 +15,7 @@ depends: [
   "base"          {>= "v0.14" & < "v0.15"}
   "ppx_sexp_conv" {>= "v0.14" & < "v0.15"}
   "dune"          {>= "2.0.0"}
-  "ppxlib"        {>= "0.11.0"}
+  "ppxlib"        {>= "0.18.0"}
 ]
 synopsis: "Printf-style format-strings for user-defined string conversion"
 description: "
diff --git a/src/ppx_custom_printf.ml b/src/ppx_custom_printf.ml
index 18ad7fd..e9ad8b3 100644
--- a/src/ppx_custom_printf.ml
+++ b/src/ppx_custom_printf.ml
@@ -264,7 +264,7 @@ let expand_format_string ~loc fmt_string =
 let expand e =
   match e.pexp_desc with
   | Pexp_apply ({ pexp_attributes = ident_attrs; _ },
-                [ (Nolabel, { pexp_desc = Pexp_constant (Pconst_string (str, _))
+                [ (Nolabel, { pexp_desc = Pexp_constant (Pconst_string (str, _, _))
                             ; pexp_loc = loc; pexp_loc_stack = _
                             ; pexp_attributes = str_attrs }) ]) ->
     assert_no_attributes ident_attrs;