diff --git a/core/src/nixpkgs.sld b/core/src/nixpkgs.sld
index e4c3089..4088575 100644
--- a/core/src/nixpkgs.sld
+++ b/core/src/nixpkgs.sld
@@ -4,7 +4,7 @@
     (scheme base) (scheme lazy) (scheme read)
     (zilch magic) (zilch nix drv) (zilch nix hash)
     (zilch nix path) (zilch zexpr)
-    (srfi 18) (srfi 128) (srfi 146)
+    (srfi 18) (srfi 128) (srfi 146) (srfi 152)
     (chicken format) (chicken process)
     json)
   (export nix-prefetch-url nixpkgs nixpkgs-eval
@@ -33,6 +33,10 @@
       (define thread (thread-start! (make-thread (lambda () (run-stderr-thread (string-append path) stderr)) "read-from-nixpkgs-raw stderr passthrough")))
       (close-port stdin)
       (define drvpath (read-line stdout))
+      ; If we get a /nix/store/[...].drv![output name]: remove the suffix.
+      (let ((loc (string-contains drvpath "!")))
+       (when loc
+         (set! drvpath (string-copy drvpath 0 loc))))
       (define-values (_ _ _) (process-wait pid #t))
       (close-port stdout)
       drvpath)