diff --git a/include/picotls.h b/include/picotls.h
index 2486ff3..6628cf1 100644
--- a/include/picotls.h
+++ b/include/picotls.h
@@ -237,6 +237,8 @@
             0xfb, 0xd5, 0x1a, 0xd2, 0xf1, 0x48, 0x98, 0xb9, 0x5b                                                                   \
     }
 
+#define PTLS_QUICINT_MAX 4611686018427387903 // (1 << 62) - 1
+
 typedef struct st_ptls_t ptls_t;
 typedef struct st_ptls_context_t ptls_context_t;
 typedef struct st_ptls_key_schedule_t ptls_key_schedule_t;