--- a/libbuild2/buildfile
+++ b/libbuild2/buildfile
@@ -86,8 +86,11 @@ build2_config_lines = [strings]
 host_config_lines = [strings]
 
 for l: $regex.replace_lines(                                                   \
+  $regex.replace_lines(                                                        \
   $config.save(),                                                              \
   '^( *(#|(config\.(test[. ]|dist\.|install\.chroot|config\.hermetic))).*|)$', \
+  [null], return_lines),                                                       \
+  '^.*'$getenv(NIX_STORE)'/[a-z0-9]{32}-.*$',                                  \
   [null])
 {
   build2_config_lines += $l