diff --git a/libbuild2-autoconf/libbuild2/autoconf/rule.cxx b/libbuild2-autoconf/libbuild2/autoconf/rule.cxx
index 4698c42..2383004 100644
--- a/libbuild2-autoconf/libbuild2/autoconf/rule.cxx
+++ b/libbuild2-autoconf/libbuild2/autoconf/rule.cxx
@@ -112,7 +112,7 @@ namespace build2
     void rule::
     process (const location& l,
              action a, const target& t,
-             depdb& dd, size_t dd_skip,
+             depdb& dd, size_t& dd_skip,
              string& s, size_t b,
              const char* nl,
              char sym,
diff --git a/libbuild2-autoconf/libbuild2/autoconf/rule.hxx b/libbuild2-autoconf/libbuild2/autoconf/rule.hxx
index 5d6fdb2..91877b3 100644
--- a/libbuild2-autoconf/libbuild2/autoconf/rule.hxx
+++ b/libbuild2-autoconf/libbuild2/autoconf/rule.hxx
@@ -30,7 +30,7 @@ namespace build2
       virtual void
       process (const location&,
                action, const target&,
-               depdb&, size_t,
+               depdb&, size_t&,
                string&, size_t,
                const char*,
                char,