diff --git a/src/compilersupport_p.h b/src/compilersupport_p.h
index 92517997..4baf9bd5 100644
--- a/src/compilersupport_p.h
+++ b/src/compilersupport_p.h
@@ -202,10 +202,14 @@
 
 #ifdef __cplusplus
 #  define CONST_CAST(t, v)  const_cast<t>(v)
-#  define CBOR_NULLPTR nullptr
 #else
 /* C-style const_cast without triggering a warning with -Wcast-qual */
 #  define CONST_CAST(t, v)  (t)(uintptr_t)(v)
+#endif
+
+#if defined(__cplusplus) || __STDC_VERSION__ >= 202311
+#  define CBOR_NULLPTR nullptr
+#else
 #  define CBOR_NULLPTR NULL
 #endif