diff --git a/core/src/nix/drv.sld b/core/src/nix/drv.sld
index 8ca9666..bf0b814 100644
--- a/core/src/nix/drv.sld
+++ b/core/src/nix/drv.sld
@@ -21,6 +21,7 @@
     derivation-args derivation-env derivation-equal?
 
     derivation-meta set-derivation-meta!
+    drv-is-fod
 
     derivation-serialize derivation-path-references derivation-path derivation-read read-drv-path
     make-fixed-output-derivation make-input-addressed-derivation make-impure-derivation make-ca-derivation