diff --git a/crates/pep508-rs/src/marker/environment.rs b/crates/pep508-rs/src/marker/environment.rs
index d9c3ee49d..54f80b394 100644
--- a/crates/pep508-rs/src/marker/environment.rs
+++ b/crates/pep508-rs/src/marker/environment.rs
@@ -1,3 +1,4 @@
+#[cfg(feature = "pyo3")]
 use std::str::FromStr;
 use std::sync::Arc;