diff --git a/libcxx/include/tgmath.h b/libcxx/include/tgmath.h
index c650917..e6f0a4a 100644
--- a/libcxx/include/tgmath.h
+++ b/libcxx/include/tgmath.h
@@ -24,13 +24,11 @@
 #endif
 
 #ifdef __cplusplus
-
-#include <ctgmath>
-
-#else  // __cplusplus
-
-#include_next <tgmath.h>
-
-#endif // __cplusplus
+#  include <ctgmath>
+#else
+#  if __has_include_next(<tgmath.h>)
+#    include_next <tgmath.h>
+#  endif
+#endif
 
 #endif // _LIBCPP_TGMATH_H