diff --git a/generator/gobject.ml b/generator/gobject.ml
index e5ae49167..8f23135ae 100644
--- a/generator/gobject.ml
+++ b/generator/gobject.ml
@@ -271,7 +271,7 @@ let generate_gobject_struct_header filename typ cols () =
 
   header_end filename
 
-let generate_gobject_struct_source filename typ cols () =
+let generate_gobject_struct_source filename typ () =
   let title = "Guestfs" ^ camel_name_of_struct typ in
   source_start ~title filename;
 
@@ -295,7 +295,7 @@ let generate_gobject_struct_source filename typ cols () =
   pr "G_DEFINE_BOXED_TYPE (%s, %s, %s_copy, %s_free)\n"
      camel_name name name name
 
-let generate_gobject_optargs_header filename name optargs f () =
+let generate_gobject_optargs_header filename name f () =
   header_start filename;
   let uc_name = String.uppercase name in
   let camel_name = camel_of_name f in
diff --git a/generator/gobject.mli b/generator/gobject.mli
index 50daac56c..0e2934e15 100644
--- a/generator/gobject.mli
+++ b/generator/gobject.mli
@@ -19,11 +19,11 @@
 val generate_gobject_doc_title : unit -> unit
 val generate_gobject_header : unit -> unit
 val generate_gobject_makefile : unit -> unit
-val generate_gobject_optargs_header : string -> string -> 'a -> Types.action -> unit -> unit
+val generate_gobject_optargs_header : string -> string -> Types.action -> unit -> unit
 val generate_gobject_optargs_source : string -> string -> Types.optargt list -> Types.action -> unit -> unit
 val generate_gobject_session_header : unit -> unit
 val generate_gobject_session_source : unit -> unit
 val generate_gobject_struct_header : string -> string -> (string * Types.field) list -> unit -> unit
-val generate_gobject_struct_source : string -> string -> 'a -> unit -> unit
+val generate_gobject_struct_source : string -> string -> unit -> unit
 val generate_gobject_tristate_header : unit -> unit
 val generate_gobject_tristate_source : unit -> unit
diff --git a/generator/main.ml b/generator/main.ml
index ca882b11a..63a5d25f0 100644
--- a/generator/main.ml
+++ b/generator/main.ml
@@ -179,7 +179,7 @@ Run it from the top source directory using the command
         sprintf "gobject/include/guestfs-gobject/%s.h" short in
       output_to filename (generate_gobject_struct_header short typ cols);
       let filename = sprintf "gobject/src/%s.c" short in
-      output_to filename (generate_gobject_struct_source short typ cols)
+      output_to filename (generate_gobject_struct_source short typ)
   ) external_structs;
   delete_except_generated "gobject/include/guestfs-gobject/struct-*.h";
   delete_except_generated "gobject/src/struct-*.c";
@@ -191,7 +191,7 @@ Run it from the top source directory using the command
       let filename =
         sprintf "gobject/include/guestfs-gobject/%s.h" short in
       output_to filename
-        (generate_gobject_optargs_header short name optargs f);
+        (generate_gobject_optargs_header short name f);
       let filename = sprintf "gobject/src/%s.c" short in
       output_to filename
         (generate_gobject_optargs_source short name optargs f)