diff --git a/core/fxcrt/widestring.cpp b/core/fxcrt/widestring.cpp
index b51ed68..813f2b8 100644
--- a/core/fxcrt/widestring.cpp
+++ b/core/fxcrt/widestring.cpp
@@ -410,7 +410,7 @@
   return *this;
 }
 
-WideString& WideString::operator=(WideString&& that) {
+WideString& WideString::operator=(WideString&& that) noexcept {
   if (m_pData != that.m_pData)
     m_pData = std::move(that.m_pData);