diff --git a/src/base/asdf.lisp b/src/base/asdf.lisp
index 4e4af217..f8196749 100644
--- a/src/base/asdf.lisp
+++ b/src/base/asdf.lisp
@@ -18,10 +18,11 @@
                   uiop:*uninteresting-compiler-conditions*)))
     (multiple-value-bind (symbols values)
         (if (find-package :cffi)
-            (values (find-symbol #.(string '#:*foreign-library-directories*) :cffi) '(nil))
+            (values (list (find-symbol #.(string '#:*foreign-library-directories*) :cffi)) '(nil))
             (values nil nil))
-      (with-standard-io-syntax
-        (let (;; Compilation fails because of CFFI types that
-              ;; can't be printed readably, so bind to NIL
-              (*print-readably* nil))
-          (funcall continuation))))))
+      (progv symbols values
+        (with-standard-io-syntax
+          (let (;; Compilation fails because of CFFI types that
+                ;; can't be printed readably, so bind to NIL
+                (*print-readably* nil))
+            (funcall continuation)))))))