diff --git a/Source/cmString.hxx b/Source/cmString.hxx
index 1994c2ce10..5e1b524441 100644
--- a/Source/cmString.hxx
+++ b/Source/cmString.hxx
@@ -518,7 +518,7 @@ public:
     *this = std::move(s);
   }
 
-  void swap(String& other)
+  void swap(String& other) noexcept
   {
     std::swap(this->string_, other.string_);
     std::swap(this->view_, other.view_);