diff --git a/src/lck-posix.c b/src/lck-posix.c
index 532505e8..c8d5e657 100644
--- a/src/lck-posix.c
+++ b/src/lck-posix.c
@@ -89,8 +89,6 @@ int mdbx_lck_downgrade(MDBX_env *env, bool complete) {
   return complete ? mdbx_lck_shared(env->me_lfd) : MDBX_SUCCESS;
 }
 
-int mdbx_lck_upgrade(MDBX_env *env) { return mdbx_lck_exclusive(env->me_lfd); }
-
 int mdbx_rpid_set(MDBX_env *env) {
   return mdbx_lck_op(env->me_lfd, F_SETLK, F_WRLCK, env->me_pid, 1);
 }
diff --git a/src/lck-windows.c b/src/lck-windows.c
index 3f4d2c80..1e9e0cc9 100644
--- a/src/lck-windows.c
+++ b/src/lck-windows.c
@@ -441,47 +441,6 @@ int mdbx_lck_downgrade(MDBX_env *env, bool complete) {
   return MDBX_SUCCESS /* 7) now at S-? (used), done */;
 }
 
-int mdbx_lck_upgrade(MDBX_env *env) {
-  /* Transite from locked state (S-E) to exclusive-write (E-E) */
-  assert(env->me_fd != INVALID_HANDLE_VALUE);
-  assert(env->me_lfd != INVALID_HANDLE_VALUE);
-
-  /* 1) must be at S-E (locked), transite to ?_E (middle) */
-  if (!funlock(env->me_lfd, LCK_LOWER))
-    mdbx_panic("%s(%s) failed: errcode %u", mdbx_func_,
-               "S-E(locked) >> ?-E(middle)", GetLastError());
-
-  /* 3) now on ?-E (middle), try E-E (exclusive-write) */
-  mdbx_jitter4testing(false);
-  if (flock(env->me_lfd, LCK_EXCLUSIVE | LCK_DONTWAIT, LCK_LOWER))
-    return MDBX_RESULT_TRUE; /* 4) got E-E (exclusive-write), done */
-
-  /* 5) still on ?-E (middle) */
-  int rc = GetLastError();
-  mdbx_jitter4testing(false);
-  if (rc != ERROR_SHARING_VIOLATION && rc != ERROR_LOCK_VIOLATION) {
-    /* 6) something went wrong, report but continue */
-    mdbx_error("%s(%s) failed: errcode %u", mdbx_func_,
-               "?-E(middle) >> E-E(exclusive-write)", rc);
-  }
-
-  /* 7) still on ?-E (middle), try restore S-E (locked) */
-  mdbx_jitter4testing(false);
-  rc = flock(env->me_lfd, LCK_SHARED | LCK_DONTWAIT, LCK_LOWER)
-           ? MDBX_RESULT_FALSE
-           : GetLastError();
-
-  mdbx_jitter4testing(false);
-  if (rc != MDBX_RESULT_FALSE) {
-    mdbx_fatal("%s(%s) failed: errcode %u", mdbx_func_,
-               "?-E(middle) >> S-E(locked)", rc);
-    return rc;
-  }
-
-  /* 8) now on S-E (locked) */
-  return MDBX_RESULT_FALSE;
-}
-
 void mdbx_lck_destroy(MDBX_env *env) {
   int rc;
 
diff --git a/src/osal.h b/src/osal.h
index 46bf82a0..0b230a4a 100644
--- a/src/osal.h
+++ b/src/osal.h
@@ -548,7 +548,6 @@ int mdbx_lck_init(MDBX_env *env);
 
 int mdbx_lck_seize(MDBX_env *env);
 int mdbx_lck_downgrade(MDBX_env *env, bool complete);
-int mdbx_lck_upgrade(MDBX_env *env);
 void mdbx_lck_destroy(MDBX_env *env);
 
 int mdbx_rdt_lock(MDBX_env *env);