diff --git a/generated/secondlife.d.luau b/generated/secondlife.d.luau
index bb30364f..749138ed 100644
--- a/generated/secondlife.d.luau
+++ b/generated/secondlife.d.luau
@@ -6,10 +6,10 @@
 ----------------------------------
 
 declare extern type quaternion with
-  x: number
-  y: number
-  z: number
-  s: number
+  read x: number
+  read y: number
+  read z: number
+  read s: number
   function __add(self, other: quaternion): quaternion
   function __sub(self, other: quaternion): quaternion
   function __mul(self, other: quaternion): quaternion
@@ -20,15 +20,15 @@ declare extern type quaternion with
 end
 
 declare extern type uuid with
-  istruthy: boolean
-  bytes: string
+  read istruthy: boolean
+  read bytes: string
   function __tostring(self): string
 end
 
 declare extern type vector with
-  x: number
-  y: number
-  z: number
+  read x: number
+  read y: number
+  read z: number
   function __add(self, other: vector): vector
   function __sub(self, other: vector): vector
   function __unm(self): vector
@@ -155,9 +155,9 @@ export type HttpRequestParams = {
 }
 
 declare extern type DetectedEvent with
-  index: number
-  valid: boolean
-  canAdjustDamage: boolean
+  read index: number
+  read valid: boolean
+  read canAdjustDamage: boolean
   function adjustDamage(self, new_damage: number): ()
   function getDamage(self): {any}
   function getGrab(self): vector
diff --git a/lsl_definitions/slua.py b/lsl_definitions/slua.py
index f8158b8b..7ff65020 100644
--- a/lsl_definitions/slua.py
+++ b/lsl_definitions/slua.py
@@ -59,8 +59,9 @@ def to_keywords_dict(self) -> dict:
             **({"value": self.value} if self.value is not None else {}),
         }
 
-    def to_luau_def(self) -> str:
-        return f"{self.name}: {self.type}"
+    def to_luau_def(self, extern: bool = False) -> str:
+        attributes = "read " if extern and self.modifiable == "read-only" else ""
+        return f"{attributes}{self.name}: {self.type}"
 
 
 @dataclasses.dataclass
@@ -318,7 +319,7 @@ def _workaround_annotated_callable_bug(self) -> None:
     def _write_extern_type_def(self, f: TextIO) -> None:
         f.write(f"declare extern type {self.name} with\n")
         for prop in self.properties.values():
-            f.write(f"  {prop.to_luau_def()}\n")
+            f.write(f"  {prop.to_luau_def(extern=True)}\n")
         for func in self.functions.values():
             func.write_luau_global_def(f, indent=1)
         for func in self.methods.values():