diff --git a/crates/plotnik-lib/src/type_system/mod.rs b/crates/plotnik-lib/src/type_system/mod.rs
index d64a746b..dea943ab 100644
--- a/crates/plotnik-lib/src/type_system/mod.rs
+++ b/crates/plotnik-lib/src/type_system/mod.rs
@@ -12,5 +12,5 @@ mod quantifier;
 
 pub use arity::Arity;
 pub use kind::TypeKind;
-pub use primitives::{PrimitiveType, TYPE_CUSTOM_START, TYPE_NODE, TYPE_STRING, TYPE_VOID};
+pub use primitives::{PrimitiveType, TYPE_STRING};
 pub use quantifier::QuantifierKind;
diff --git a/crates/plotnik-lib/src/type_system/primitives.rs b/crates/plotnik-lib/src/type_system/primitives.rs
index 1a6f747d..5dfed68d 100644
--- a/crates/plotnik-lib/src/type_system/primitives.rs
+++ b/crates/plotnik-lib/src/type_system/primitives.rs
@@ -12,9 +12,6 @@ pub const TYPE_NODE: u16 = 1;
 /// Index for the String type (extracted source text).
 pub const TYPE_STRING: u16 = 2;
 
-/// First index available for user-defined/composite types.
-pub const TYPE_CUSTOM_START: u16 = 3;
-
 /// Primitive type enumeration.
 ///
 /// These are the builtin scalar types that don't require