diff --git a/crates/ailang-check/src/lib.rs b/crates/ailang-check/src/lib.rs
index cde5498..613b930 100644
--- a/crates/ailang-check/src/lib.rs
+++ b/crates/ailang-check/src/lib.rs
@@ -1276,7 +1276,7 @@ fn check_type_def(td: &TypeDef, env: &Env) -> Result<()> {
 fn check_type_well_formed(t: &Type, env: &Env) -> Result<()> {
     match t {
         Type::Con { name, args } => {
-            let is_primitive = matches!(name.as_str(), "Int" | "Bool" | "Unit" | "Str");
+            let is_primitive = ailang_core::primitives::is_primitive_name(name);
             if is_primitive {
                 if !args.is_empty() {
                     return Err(CheckError::UnknownType(format!(
@@ -2258,7 +2258,7 @@ fn qualify_local_types(t: &Type, owner_module: &str, local_types: &IndexMap<Stri
         Type::Con { name, args } => {
             let qualified_name = if name.contains('.') {
                 name.clone()
-            } else if matches!(name.as_str(), "Int" | "Bool" | "Unit" | "Str") {
+            } else if ailang_core::primitives::is_primitive_name(name) {
                 name.clone()
             } else if local_types.contains_key(name) {
                 format!("{owner_module}.{name}")
diff --git a/crates/ailang-check/src/linearity.rs b/crates/ailang-check/src/linearity.rs
index d304a3f..064d98b 100644
--- a/crates/ailang-check/src/linearity.rs
+++ b/crates/ailang-check/src/linearity.rs
@@ -140,7 +140,7 @@ use std::collections::HashMap;
 /// == 0`.
 fn is_heap_type(t: &Type) -> bool {
     match t {
-        Type::Con { name, .. } => !matches!(name.as_str(), "Int" | "Bool" | "Str" | "Unit"),
+        Type::Con { name, .. } => !ailang_core::primitives::is_primitive_name(name),
         // Type::Var (a polymorphic param) is conservatively heap —
         // it could instantiate to a heap type at the call site.
         Type::Var { .. } => true,
diff --git a/crates/ailang-codegen/src/subst.rs b/crates/ailang-codegen/src/subst.rs
index bbdcfe9..b83d1eb 100644
--- a/crates/ailang-codegen/src/subst.rs
+++ b/crates/ailang-codegen/src/subst.rs
@@ -166,7 +166,7 @@ pub(crate) fn qualify_local_types_codegen(
         Type::Con { name, args } => {
             let qualified = if name.contains('.') {
                 name.clone()
-            } else if matches!(name.as_str(), "Int" | "Bool" | "Unit" | "Str") {
+            } else if ailang_core::primitives::is_primitive_name(name) {
                 name.clone()
             } else if owner_local_types.contains(name) {
                 format!("{owner_module}.{name}")