diff --git a/napi-inl.h b/napi-inl.h
index 40959d8e1..4f532c77b 100644
--- a/napi-inl.h
+++ b/napi-inl.h
@@ -1078,7 +1078,7 @@ inline bool Object::Delete(uint32_t index) {
   return result;
 }
 
-inline Array Object::GetPropertyNames() {
+inline Array Object::GetPropertyNames() const {
   napi_value result;
   napi_status status = napi_get_property_names(_env, _value, &result);
   NAPI_THROW_IF_FAILED(_env, status, Array());
diff --git a/napi.h b/napi.h
index 16d09943a..22fbd2de9 100644
--- a/napi.h
+++ b/napi.h
@@ -601,7 +601,7 @@ namespace Napi {
       uint32_t index ///< Property / element index
     );
 
-    Array GetPropertyNames(); ///< Get all property names
+    Array GetPropertyNames() const; ///< Get all property names
 
     /// Defines a property on the object.
     void DefineProperty(