diff --git a/crates/typst/src/foundations/label.rs b/crates/typst/src/foundations/label.rs
index 91ab572d4..53914c358 100644
--- a/crates/typst/src/foundations/label.rs
+++ b/crates/typst/src/foundations/label.rs
@@ -26,7 +26,8 @@ use crate::util::PicoStr;
 ///
 /// # Syntax
 /// This function also has dedicated syntax: You can create a label by enclosing
-/// its name in angle brackets. This works both in markup and code.
+/// its name in angle brackets. This works both in markup and code. A label's
+/// name can contain letters, numbers, `_`, `-`, `:`, and `.`.
 ///
 /// Currently, labels can only be attached to elements in markup mode, not in
 /// code mode. This might change in the future.