diff --git a/source/scriptinterface/ScriptInterface.cpp b/source/scriptinterface/ScriptInterface.cpp
index d57cbafb05..a0eb13da16 100644
--- a/source/scriptinterface/ScriptInterface.cpp
+++ b/source/scriptinterface/ScriptInterface.cpp
@@ -564,9 +564,9 @@ void ScriptInterface::DefineCustomObjectType(JSClass *clasp, JSNative constructo
 	m_CustomObjectTypes[typeName] = std::move(type);
 }
 
-JSObject* ScriptInterface::CreateCustomObject(const std::string & typeName)
+JSObject* ScriptInterface::CreateCustomObject(const std::string& typeName) const
 {
-	std::map < std::string, CustomType > ::iterator it = m_CustomObjectTypes.find(typeName);
+	std::map<std::string, CustomType>::const_iterator it = m_CustomObjectTypes.find(typeName);
 
 	if (it == m_CustomObjectTypes.end())
 		throw PSERROR_Scripting_TypeDoesNotExist();
diff --git a/source/scriptinterface/ScriptInterface.h b/source/scriptinterface/ScriptInterface.h
index 047e96a658..d2c216816f 100644
--- a/source/scriptinterface/ScriptInterface.h
+++ b/source/scriptinterface/ScriptInterface.h
@@ -162,7 +162,7 @@ public:
 	template<typename T0, typename T1, typename T2>
 	bool CallFunctionVoid(JS::HandleValue val, const char* name, const T0& a0, const T1& a1, const T2& a2);
 
-	JSObject* CreateCustomObject(const std::string & typeName);
+	JSObject* CreateCustomObject(const std::string & typeName) const;
 	void DefineCustomObjectType(JSClass *clasp, JSNative constructor, uint minArgs, JSPropertySpec *ps, JSFunctionSpec *fs, JSPropertySpec *static_ps, JSFunctionSpec *static_fs);
 
 	jsval GetGlobalObject();