diff --git a/compiler/builtins/src/std.rs b/compiler/builtins/src/std.rs
index 438fa32944..489fd3ae59 100644
--- a/compiler/builtins/src/std.rs
+++ b/compiler/builtins/src/std.rs
@@ -75,17 +75,19 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         ),
     );
 
-    // addChecked : Num a, Num a -> Result (Num a) [ Overflow ]*
-    let overflow = SolvedType::TagUnion(
-        vec![(TagName::Global("Overflow".into()), vec![])],
-        Box::new(SolvedType::Wildcard),
-    );
+    fn overflow() -> SolvedType {
+        SolvedType::TagUnion(
+            vec![(TagName::Global("Overflow".into()), vec![])],
+            Box::new(SolvedType::Wildcard),
+        )
+    }
 
+    // addChecked : Num a, Num a -> Result (Num a) [ Overflow ]*
     add_type(
         Symbol::NUM_ADD_CHECKED,
         top_level_function(
             vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
-            Box::new(result_type(num_type(flex(TVAR1)), overflow.clone())),
+            Box::new(result_type(num_type(flex(TVAR1)), overflow())),
         ),
     );
 
@@ -115,7 +117,7 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
         Symbol::NUM_SUB_CHECKED,
         top_level_function(
             vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
-            Box::new(result_type(num_type(flex(TVAR1)), overflow)),
+            Box::new(result_type(num_type(flex(TVAR1)), overflow())),
         ),
     );