diff --git a/src/font/system.rs b/src/font/system.rs
index 7d7e786..299bb99 100644
--- a/src/font/system.rs
+++ b/src/font/system.rs
@@ -7,10 +7,10 @@ use core::ops::{Deref, DerefMut};
 
 type BuildHasher = core::hash::BuildHasherDefault<rustc_hash::FxHasher>;
 
-#[cfg(feature = "no_std")]
-type HashMap<K, V> = hashbrown::HashMap<K, V, BuildHasher>;
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 type HashMap<K, V> = std::collections::HashMap<K, V, BuildHasher>;
+#[cfg(not(feature = "std"))]
+type HashMap<K, V> = hashbrown::HashMap<K, V, BuildHasher>;
 
 // re-export fontdb and rustybuzz
 pub use fontdb;
diff --git a/src/lib.rs b/src/lib.rs
index 3a16321..ac684b9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -91,9 +91,11 @@
 // Ensure numbers are readable
 #![warn(clippy::unreadable_literal)]
 #![cfg_attr(not(feature = "std"), no_std)]
-
 extern crate alloc;
 
+#[cfg(not(any(feature = "std", feature = "no_std")))]
+compile_error!("Either the `std` or `no_std` feature must be enabled");
+
 pub use self::attrs::*;
 mod attrs;