--- a/layout/style/ServoBindingList.h
+++ b/layout/style/ServoBindingList.h
@@ -661,17 +661,17 @@ SERVO_BINDING_FUNC(Servo_ProcessInvalida
                    RawGeckoElementBorrowed element,
                    const mozilla::ServoElementSnapshotTable* snapshots)
 
 
 SERVO_BINDING_FUNC(Servo_HasPendingRestyleAncestor, bool,
                    RawGeckoElementBorrowed element)
 
 SERVO_BINDING_FUNC(Servo_GetArcStringData, void,
-                   const RustString*, uint8_t** chars, uint32_t* len);
+                   const RustString*, uint8_t const** chars, uint32_t* len);
 SERVO_BINDING_FUNC(Servo_ReleaseArcStringData, void,
                    const mozilla::ServoRawOffsetArc<RustString>* string);
 SERVO_BINDING_FUNC(Servo_CloneArcStringData, mozilla::ServoRawOffsetArc<RustString>,
                    const mozilla::ServoRawOffsetArc<RustString>* string);
 
 // AddRef / Release functions
 #define SERVO_ARC_TYPE(name_, type_)                                \
   SERVO_BINDING_FUNC(Servo_##name_##_AddRef, void, type_##Borrowed) \