diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index 7dc4c9ad..c24e583a 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -20,5 +20,5 @@ jobs:
         run: cargo build --verbose
       - name: Run tests
         run: cargo test --verbose
-      - name: Run no default
-        run: cargo test --verbose --no-default-features
+      - name: Build no default
+        run: cargo build --verbose --no-default-features
diff --git a/ndc_stdlib/Cargo.toml b/ndc_stdlib/Cargo.toml
index fe7bf513..84884144 100644
--- a/ndc_stdlib/Cargo.toml
+++ b/ndc_stdlib/Cargo.toml
@@ -11,15 +11,20 @@ ndc_lib = { workspace = true }
 ndc_macros.workspace = true
 num.workspace = true
 once_cell.workspace = true
-rand.workspace = true
-regex.workspace = true
-serde_json = { workspace = true }
 tap.workspace = true
 
+# Optional
+rand = { workspace = true, optional = true }
+regex = { workspace = true, optional = true }
+serde_json = { workspace = true, optional = true }
+
 # Crypto
 md5 = { version = "0.8.0", optional = true }
 sha1 = { version = "0.10.6", optional = true }
 
 [features]
-default = ["crypto"]
+default = ["crypto", "rand", "regex", "serde"]
 crypto = ["dep:md5", "dep:sha1"]
+rand = ["dep:rand"]
+regex = ["dep:regex"]
+serde = ["dep:serde_json"]
diff --git a/ndc_stdlib/src/lib.rs b/ndc_stdlib/src/lib.rs
index 41270177..b1acc2c2 100644
--- a/ndc_stdlib/src/lib.rs
+++ b/ndc_stdlib/src/lib.rs
@@ -9,15 +9,18 @@ pub mod hash_map;
 pub mod heap;
 pub mod list;
 pub mod math;
-pub mod rand;
-pub mod regex;
 pub mod sequence;
-pub mod serde;
 pub mod string;
 pub mod value;
 
 #[cfg(feature = "crypto")]
 pub mod crypto;
+#[cfg(feature = "rand")]
+pub mod rand;
+#[cfg(feature = "regex")]
+pub mod regex;
+#[cfg(feature = "serde")]
+pub mod serde;
 
 pub fn register(env: &mut Environment) {
     aoc::register(env);
@@ -32,10 +35,13 @@ pub fn register(env: &mut Environment) {
     list::register(env);
     math::f64::register(env);
     math::register(env);
+    #[cfg(feature = "rand")]
     rand::register(env);
+    #[cfg(feature = "regex")]
     regex::register(env);
     sequence::extra::register(env);
     sequence::register(env);
+    #[cfg(feature = "serde")]
     serde::register(env);
     string::register(env);
     value::register(env);