1 files changed, 10 insertions, 0 deletions
diff --git a/src/library/mod.rs b/src/library/mod.rs
index 313d423b..1c97f529 100644
--- a/src/library/mod.rs
+++ b/src/library/mod.rs
@@ -26,6 +26,7 @@ mod utility;
 /// Helpful imports for creating library functionality.
 mod prelude {
     pub use std::fmt::{self, Debug, Formatter};
+    pub use std::num::NonZeroUsize;
     pub use std::rc::Rc;
 
     pub use typst_macros::properties;
@@ -172,6 +173,15 @@ castable! {
 }
 
 castable! {
+    prelude::NonZeroUsize,
+    Expected: "positive integer",
+    Value::Int(int) => int
+        .try_into()
+        .and_then(|n: usize| n.try_into())
+        .map_err(|_| "must be positive")?,
+}
+
+castable! {
     String,
     Expected: "string",
     Value::Str(string) => string.into(),