diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index aba0724d..5e18a493 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -39,7 +39,7 @@ endforeach ()
 check_cxx_source_compiles("
   #include <type_traits>
   class C { void operator=(const C&); };
-  int main() { static_assert(std::is_copy_assignable<C>::value, \"\"); }"
+  int main() { static_assert(!std::is_copy_assignable<C>::value, \"\"); }"
   HAVE_TYPE_TRAITS)
 if (HAVE_TYPE_TRAITS)
   add_definitions(-DFMT_USE_TYPE_TRAITS=1)