diff --git a/phf/src/lib.rs b/phf/src/lib.rs
index 1d8e4a84..f58e687e 100644
--- a/phf/src/lib.rs
+++ b/phf/src/lib.rs
@@ -5,7 +5,6 @@
 //! the documentation of those crates for more details.
 #![doc(html_root_url="https://sfackler.github.io/rust-phf/doc/v0.7.13")]
 #![warn(missing_docs)]
-#![cfg_attr(feature = "core", feature(no_std, core_slice_ext))]
 #![cfg_attr(feature = "core", no_std)]
 
 #[cfg(not(feature = "core"))]
diff --git a/phf_shared/src/lib.rs b/phf_shared/src/lib.rs
index 8f8a6f62..00bcb109 100644
--- a/phf_shared/src/lib.rs
+++ b/phf_shared/src/lib.rs
@@ -1,5 +1,4 @@
 #![doc(html_root_url="http://sfackler.github.io/rust-phf/doc/v0.7.13")]
-#![cfg_attr(feature = "core", feature(no_std, core_slice_ext, core_str_ext))]
 #![cfg_attr(feature = "core", no_std)]
 #[cfg(not(feature = "core"))]
 extern crate std as core;