diff --git a/mdbx.h b/mdbx.h
index 887358b2..4e0d6b9a 100644
--- a/mdbx.h
+++ b/mdbx.h
@@ -1446,12 +1446,49 @@ enum MDBX_txn_flags_t {
   MDBX_TXN_TRY = UINT32_C(0x10000000),
 
   /** Exactly the same as \ref MDBX_NOMETASYNC,
-   * but for this transaction only */
+   * but for this transaction only. */
   MDBX_TXN_NOMETASYNC = MDBX_NOMETASYNC,
 
   /** Exactly the same as \ref MDBX_SAFE_NOSYNC,
-   * but for this transaction only */
-  MDBX_TXN_NOSYNC = MDBX_SAFE_NOSYNC
+   * but for this transaction only. */
+  MDBX_TXN_NOSYNC = MDBX_SAFE_NOSYNC,
+
+  /* Transaction state flags ---------------------------------------------- */
+
+  /** Transaction is invalid.
+   * \note Transaction state flag. Returned from \ref mdbx_txn_flags()
+   * but can't be used with \ref mdbx_txn_begin(). */
+  MDBX_TXN_INVALID = 0x80000000,
+
+  /** Transaction is finished or never began.
+   * \note Transaction state flag. Returned from \ref mdbx_txn_flags()
+   * but can't be used with \ref mdbx_txn_begin(). */
+  MDBX_TXN_FINISHED = 0x01,
+
+  /** Transaction is unusable after an error.
+   * \note Transaction state flag. Returned from \ref mdbx_txn_flags()
+   * but can't be used with \ref mdbx_txn_begin(). */
+  MDBX_TXN_ERROR = 0x02,
+
+  /** Transaction must write, even if dirty list is empty.
+   * \note Transaction state flag. Returned from \ref mdbx_txn_flags()
+   * but can't be used with \ref mdbx_txn_begin(). */
+  MDBX_TXN_DIRTY = 0x04,
+
+  /** Transaction or a parent has spilled pages.
+   * \note Transaction state flag. Returned from \ref mdbx_txn_flags()
+   * but can't be used with \ref mdbx_txn_begin(). */
+  MDBX_TXN_SPILLS = 0x08,
+
+  /** Transaction has a nested child transaction.
+   * \note Transaction state flag. Returned from \ref mdbx_txn_flags()
+   * but can't be used with \ref mdbx_txn_begin(). */
+  MDBX_TXN_HAS_CHILD = 0x10,
+
+  /** Most operations on the transaction are currently illegal.
+   * \note Transaction state flag. Returned from \ref mdbx_txn_flags()
+   * but can't be used with \ref mdbx_txn_begin(). */
+  MDBX_TXN_BLOCKED = MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_HAS_CHILD
 };
 #ifndef __cplusplus
 typedef enum MDBX_txn_flags_t MDBX_txn_flags_t;
@@ -3429,7 +3466,7 @@ mdbx_txn_env(const MDBX_txn *txn);
 /** \brief Return the transaction's flags.
  * \ingroup c_transactions
  *
- * This returns the flags associated with this transaction.
+ * This returns the flags, including internal, associated with this transaction.
  *
  * \param [in] txn  A transaction handle returned by \ref mdbx_txn_begin().
  *
diff --git a/src/core.c b/src/core.c
index 32821f87..d6711fb9 100644
--- a/src/core.c
+++ b/src/core.c
@@ -8434,8 +8434,11 @@ uint64_t mdbx_txn_id(const MDBX_txn *txn) {
 }
 
 int mdbx_txn_flags(const MDBX_txn *txn) {
-  if (unlikely(!txn || txn->mt_signature != MDBX_MT_SIGNATURE))
+  if (unlikely(!txn || txn->mt_signature != MDBX_MT_SIGNATURE)) {
+    assert((-1 & (int)MDBX_TXN_INVALID) != 0);
     return -1;
+  }
+  assert(0 == (int)(txn->mt_flags & MDBX_TXN_INVALID));
   return txn->mt_flags;
 }
 
diff --git a/src/internals.h b/src/internals.h
index d255a955..ce1d6098 100644
--- a/src/internals.h
+++ b/src/internals.h
@@ -895,16 +895,6 @@ struct MDBX_txn {
   /* Additional flag for mdbx_sync_locked() */
 #define MDBX_SHRINK_ALLOWED UINT32_C(0x40000000)
 
-  /* internal txn flags */
-#define MDBX_TXN_FINISHED 0x01  /* txn is finished or never began */
-#define MDBX_TXN_ERROR 0x02     /* txn is unusable after an error */
-#define MDBX_TXN_DIRTY 0x04     /* must write, even if dirty list is empty */
-#define MDBX_TXN_SPILLS 0x08    /* txn or a parent has spilled pages */
-#define MDBX_TXN_HAS_CHILD 0x10 /* txn has an MDBX_txn.mt_child */
-  /* most operations on the txn are currently illegal */
-#define MDBX_TXN_BLOCKED                                                       \
-  (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_HAS_CHILD)
-
 #define TXN_FLAGS                                                              \
   (MDBX_TXN_FINISHED | MDBX_TXN_ERROR | MDBX_TXN_DIRTY | MDBX_TXN_SPILLS |     \
    MDBX_TXN_HAS_CHILD)
@@ -912,7 +902,7 @@ struct MDBX_txn {
 #if (TXN_FLAGS & (MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS)) ||       \
     ((MDBX_TXN_RW_BEGIN_FLAGS | MDBX_TXN_RO_BEGIN_FLAGS | TXN_FLAGS) &         \
      MDBX_SHRINK_ALLOWED)
-#error "Oops, some flags overlapped or wrong"
+#error "Oops, some txn flags overlapped or wrong"
 #endif
   uint32_t mt_flags;