Forwarded: https://github.com/dholroyd/four-cc/issues/22
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -289,6 +289,7 @@
     }
 
     #[cfg(feature = "serde")]
+    #[cfg(feature = "std")]
     #[test]
     fn deserialize() {
         use std::str::FromStr;