diff --git a/purl/src/lib.rs b/purl/src/lib.rs
index 5ec66fa..37a5223 100644
--- a/purl/src/lib.rs
+++ b/purl/src/lib.rs
@@ -9,6 +9,7 @@ pub use format::*;
 pub use package_type::*;
 pub use parse::*;
 pub use qualifiers::Qualifiers;
+#[cfg(feature = "smartstring")]
 use smartstring::{LazyCompact, SmartString, SmartStringMode};
 
 mod builder;
@@ -181,6 +182,7 @@ impl<'a> PurlShape for Cow<'a, str> {
 /// Without type-specific functionality, it's possible to create PURLs that have
 /// incorrect capitalization or are missing a required namespace or required
 /// qualifiers.
+#[cfg(feature = "smartstring")]
 impl<M> PurlShape for SmartString<M>
 where
     M: SmartStringMode,