diff --git a/tools/genstubs.scm b/tools/genstubs.scm
index b38b1704..daf8a684 100755
--- a/tools/genstubs.scm
+++ b/tools/genstubs.scm
@@ -982,7 +982,8 @@
 
 (define (write-func func)
   (cat "static sexp " (func-stub-name func)
-       " (sexp ctx" (write-parameters (func-scheme-args func)) ") {\n")
+       " (sexp ctx sexp_api_params(self, n)"
+       (write-parameters (func-scheme-args func)) ") {\n")
   (write-locals func)
   (write-validators (func-scheme-args func))
   (write-temporaries func)