diff --git a/addon/-private/fields/has-many.ts b/addon/-private/fields/has-many.ts
index 0d814e22..2fd0d52d 100644
--- a/addon/-private/fields/has-many.ts
+++ b/addon/-private/fields/has-many.ts
@@ -36,7 +36,10 @@ export default function hasMany(
       def === undefined
     );
 
-    assert('@hasMany() requires a `type` argument.', relDef.type !== undefined);
+    assert(
+      '@hasMany() requires a `type` argument.',
+      relDef?.type !== undefined
+    );
   }
 
   relDef.kind = 'hasMany';
diff --git a/addon/-private/fields/has-one.ts b/addon/-private/fields/has-one.ts
index 63a08b7a..4d80ed45 100644
--- a/addon/-private/fields/has-one.ts
+++ b/addon/-private/fields/has-one.ts
@@ -35,7 +35,7 @@ export default function hasOne(
       def === undefined
     );
 
-    assert('@hasOne() requires a `type` argument.', relDef.type !== undefined);
+    assert('@hasOne() requires a `type` argument.', relDef?.type !== undefined);
   }
 
   relDef.kind = 'hasOne';