diff --git a/src/cargo/util/config/de.rs b/src/cargo/util/config/de.rs
index 758f5c23f13..a70cd0dce80 100644
--- a/src/cargo/util/config/de.rs
+++ b/src/cargo/util/config/de.rs
@@ -527,7 +527,7 @@ impl<'de, 'config> de::MapAccess<'de> for ValueDeserializer<'config> {
                 seed.deserialize(Tuple2Deserializer(0i32, path.to_string_lossy()))
             }
             Definition::Environment(env) => {
-                seed.deserialize(Tuple2Deserializer(1i32, env.as_ref()))
+                seed.deserialize(Tuple2Deserializer(1i32, env.as_str()))
             }
             Definition::Cli => seed.deserialize(Tuple2Deserializer(2i32, "")),
         }