diff --git a/Cargo.toml b/Cargo.toml
index 84c950f..614b66a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -21,7 +21,7 @@ unicode-linebreak = "0.1.4"
 unicode-script = "0.5.5"
 unicode-segmentation = "1.10.0"
 rangemap = "1.2.0"
-hashbrown = { version = "0.14.0", default-features = false }
+hashbrown = { version = "0.14.0", optional = true, default-features = false }
 rustc-hash = { version = "1.1.0", default-features = false }
 
 [dependencies.unicode-bidi]
@@ -33,6 +33,7 @@ features = ["hardcoded-data"]
 default = ["std", "swash"]
 no_std = [
   "rustybuzz/libm",
+  "hashbrown",
 ]
 std = [
   "fontdb/memmap",
diff --git a/ci.sh b/ci.sh
index c867b6c..b746320 100755
--- a/ci.sh
+++ b/ci.sh
@@ -13,20 +13,20 @@ cargo fmt --check
 echo Build with default features
 build
 
-echo Build with no default features
-build --no-default-features
+echo Build with only no_std feature
+build --no-default-features --features no_std
 
 echo Build with only std feature
 build --no-default-features --features std
 
-echo Build with only swash feature
-build --no-default-features --features swash
+echo Build with only std and swash features
+build --no-default-features --features std,swash
 
-echo Build with only syntect feature
-build --no-default-features --features syntect
+echo Build with only std and syntect features
+build --no-default-features --features std,syntect
 
-echo Build with only vi feature
-build --no-default-features --features vi
+echo Build with only std and vi features
+build --no-default-features --features std,vi
 
 echo Build with all features
 build --all-features
diff --git a/src/font/system.rs b/src/font/system.rs
index 1152cd2..299bb99 100644
--- a/src/font/system.rs
+++ b/src/font/system.rs
@@ -3,10 +3,14 @@ use alloc::string::String;
 use alloc::sync::Arc;
 use alloc::vec::Vec;
 use core::fmt;
-use core::hash::BuildHasherDefault;
 use core::ops::{Deref, DerefMut};
 
-type HashMap<K, V> = hashbrown::HashMap<K, V, BuildHasherDefault<rustc_hash::FxHasher>>;
+type BuildHasher = core::hash::BuildHasherDefault<rustc_hash::FxHasher>;
+
+#[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;