`__builtin_types_compatible_p` is only available in C (not in C++)
diff --git a/include/picotls.h b/include/picotls.h
index e5c52ee..3012ab8 100644
--- a/include/picotls.h
+++ b/include/picotls.h
@@ -52,7 +52,7 @@
* best coverage. This macro is for preventing misuse going into the master branch, having it work one of the compilers supported in
* our CI is enough.
*/
-#if (defined(__clang__) && __clang_major__ >= 10) || __GNUC__ >= 6
+#if ((defined(__clang__) && __clang_major__ >= 10) || __GNUC__ >= 6) && !defined(__cplusplus)
#define PTLS_ASSERT_IS_ARRAY_EXPR(a) PTLS_BUILD_ASSERT_EXPR(__builtin_types_compatible_p(__typeof__(a[0])[], __typeof__(a)))
#else
#define PTLS_ASSERT_IS_ARRAY_EXPR(a) 1
