diff --git a/lang/rust/src/resolver.sld b/lang/rust/src/resolver.sld
index fd7113f..f28b8d5 100644
--- a/lang/rust/src/resolver.sld
+++ b/lang/rust/src/resolver.sld
@@ -476,7 +476,7 @@
        ; Collect the necessary bits, and build the build script.
        (let*-values
          (((build-script) (cdr (resolved-package-build-data-rlib (resolved-package-build-data (resolved-package-build-script resolved)))))
-          ((rewritten-features) (map (lambda (feature) (cons (string-map upcase-underscore (string-append "CARGO_FEATURE_" feature)) "")) (resolved-package-enabled-features resolved)))
+          ((rewritten-features) (map (lambda (feature) (cons (string-map upcase-underscore (string-append "CARGO_FEATURE_" feature)) "1")) (resolved-package-enabled-features resolved)))
           ((runner-outdir runner-outpath)
            (call-runner build-script crate-root
              #~(