diff --git a/sqlx-core/src/mock.rs b/sqlx-core/src/mock.rs
index 84937208..9e5f19cd 100644
--- a/sqlx-core/src/mock.rs
+++ b/sqlx-core/src/mock.rs
@@ -98,6 +98,7 @@ impl MockStream {
     }
 }
 
+#[cfg(feature = "async")]
 impl crate::Async for Mock {}
 
 impl<'s> IoStream<'s, Mock> for MockStream {