diff --git a/sha1-checked/Cargo.toml b/sha1-checked/Cargo.toml
index b6e69623..5e424e2a 100644
--- a/sha1-checked/Cargo.toml
+++ b/sha1-checked/Cargo.toml
@@ -14,7 +14,7 @@ rust-version = "1.72"
 
 [dependencies]
 digest = "=0.11.0-pre.8"
-sha1 = { version = "=0.11.0-pre.3", features = [], path = "../sha1" }
+sha1 = { version = "=0.11.0-pre.3", default-features = false, path = "../sha1" }
 
 [dev-dependencies]
 digest = { version = "=0.11.0-pre.8", features = ["dev"] }
diff --git a/sha1-checked/src/lib.rs b/sha1-checked/src/lib.rs
index 25baf66e..c5475bca 100644
--- a/sha1-checked/src/lib.rs
+++ b/sha1-checked/src/lib.rs
@@ -23,9 +23,6 @@ pub use digest::{self, Digest};
 
 use core::slice::from_ref;
 
-#[cfg(feature = "std")]
-extern crate std;
-
 #[cfg(feature = "zeroize")]
 use digest::zeroize::{Zeroize, ZeroizeOnDrop};
 use digest::{
diff --git a/sha1/src/lib.rs b/sha1/src/lib.rs
index a17886a7..d84b001d 100644
--- a/sha1/src/lib.rs
+++ b/sha1/src/lib.rs
@@ -26,9 +26,6 @@ use digest::const_oid::{AssociatedOid, ObjectIdentifier};
 #[cfg(feature = "zeroize")]
 use digest::zeroize::{Zeroize, ZeroizeOnDrop};
 
-#[cfg(feature = "std")]
-extern crate std;
-
 mod compress;
 
 pub use compress::compress;