diff --git a/mdbx.h b/mdbx.h
index 1e71f1ad..b5d85921 100644
--- a/mdbx.h
+++ b/mdbx.h
@@ -2880,10 +2880,15 @@ LIBMDBX_API int mdbx_env_get_fd(const MDBX_env *env, mdbx_filehandle_t *fd);
  *          some possible errors are:
  * \retval MDBX_EINVAL    An invalid parameter was specified,
  *                        or the environment has an active write transaction.
- * \retval MDBX_EPERM     Specific for Windows: Shrinking was disabled before
- *                        and now it wanna be enabled, but there are reading
- *                        threads that don't use the additional `SRWL` (that
- *                        is required to avoid Windows issues).
+ * \retval MDBX_EPERM     Two specific cases for Windows:
+ *                        1) Shrinking was disabled before via geometry settings
+ *                        and now it enabled, but there are reading threads that
+ *                        don't use the additional `SRWL` (which is required to
+ *                        avoid Windows issues).
+ *                        2) Temporary close memory mapped is required to change
+ *                        geometry, but there read transaction(s) is running
+ *                        and no corresponding thread(s) could be suspended
+ *                        since the \ref MDBX_NOTLS mode is used.
  * \retval MDBX_EACCESS   The environment opened in read-only.
  * \retval MDBX_MAP_FULL  Specified size smaller than the space already
  *                        consumed by the environment.
diff --git a/src/core.c b/src/core.c
index 9cb5f513..5eb3190c 100644
--- a/src/core.c
+++ b/src/core.c
@@ -6234,7 +6234,7 @@ bailout:
     }
 #endif /* MDBX_USE_VALGRIND */
   } else {
-    if (rc != MDBX_UNABLE_EXTEND_MAPSIZE && rc != MDBX_RESULT_TRUE) {
+    if (rc != MDBX_UNABLE_EXTEND_MAPSIZE && rc != MDBX_EPERM) {
       mdbx_error("failed resize datafile/mapping: "
                  "present %" PRIuPTR " -> %" PRIuPTR ", "
                  "limit %" PRIuPTR " -> %" PRIuPTR ", errcode %d",
@@ -8716,7 +8716,7 @@ static int mdbx_txn_end(MDBX_txn *txn, const unsigned mode) {
         /* undo resize performed by child txn */
         rc = mdbx_mapresize_implicit(env, parent->mt_next_pgno,
                                      parent->mt_geo.now, parent->mt_geo.upper);
-        if (rc == MDBX_RESULT_TRUE) {
+        if (rc == MDBX_EPERM) {
           /* unable undo resize (it is regular for Windows),
            * therefore promote size changes from child to the parent txn */
           mdbx_warning("unable undo resize performed by child txn, promote to "
@@ -11256,7 +11256,7 @@ static int mdbx_sync_locked(MDBX_env *env, unsigned flags,
                  pending->mm_geo.now, shrink);
     rc = mdbx_mapresize_implicit(env, pending->mm_geo.next, pending->mm_geo.now,
                                  pending->mm_geo.upper);
-    if (MDBX_IS_ERROR(rc))
+    if (rc != MDBX_SUCCESS && rc != MDBX_EPERM)
       goto fail;
     mdbx_assert(env, meta_checktxnid(env, target, true));
   }
diff --git a/src/osal.c b/src/osal.c
index 51a170af..f0cb13b5 100644
--- a/src/osal.c
+++ b/src/osal.c
@@ -1619,7 +1619,7 @@ MDBX_INTERNAL_FUNC int mdbx_mresize(const int flags, mdbx_mmap_t *map,
    *  - extend read-only mapping;
    * Therefore we should unmap/map entire section. */
   if ((flags & MDBX_MRESIZE_MAY_UNMAP) == 0)
-    return MDBX_RESULT_TRUE;
+    return MDBX_EPERM;
 
   /* Unpoisoning is required for ASAN to avoid false-positive diagnostic
    * when this memory will re-used by malloc or another mmapping.
@@ -1729,7 +1729,7 @@ retry_mapview:;
     if (map->address && (size != map->current || limit != map->limit)) {
       /* try remap with previously size and limit,
        * but will return MDBX_UNABLE_EXTEND_MAPSIZE on success */
-      rc = (limit > map->limit) ? MDBX_UNABLE_EXTEND_MAPSIZE : MDBX_RESULT_TRUE;
+      rc = (limit > map->limit) ? MDBX_UNABLE_EXTEND_MAPSIZE : MDBX_EPERM;
       size = map->current;
       ReservedSize = limit = map->limit;
       goto retry_file_and_section;
@@ -1753,8 +1753,7 @@ retry_mapview:;
   if (flags & MDBX_RDONLY) {
     map->current = (map->filesize > limit) ? limit : (size_t)map->filesize;
     if (map->current != size)
-      rc =
-          (size > map->current) ? MDBX_UNABLE_EXTEND_MAPSIZE : MDBX_RESULT_TRUE;
+      rc = (size > map->current) ? MDBX_UNABLE_EXTEND_MAPSIZE : MDBX_EPERM;
   } else {
     if (map->filesize != size) {
       rc = mdbx_ftruncate(map->fd, size);
diff --git a/test/jitter.cc b/test/jitter.cc
index b51c8124..2c781d7f 100644
--- a/test/jitter.cc
+++ b/test/jitter.cc
@@ -115,8 +115,7 @@ bool testcase_jitter::run() {
             db_guard.get(), -1, -1,
             coin4size ? upper_limit * 2 / 3 : upper_limit * 3 / 2, -1, -1, -1);
         if (err != MDBX_SUCCESS && err != MDBX_UNABLE_EXTEND_MAPSIZE &&
-            err != MDBX_MAP_FULL && err != MDBX_TOO_LARGE &&
-            err != MDBX_RESULT_TRUE)
+            err != MDBX_MAP_FULL && err != MDBX_TOO_LARGE && err != MDBX_EPERM)
           failure_perror("mdbx_env_set_geometry-1", err);
       }
     }
@@ -127,8 +126,7 @@ bool testcase_jitter::run() {
           db_guard.get(), -1, -1,
           !coin4size ? upper_limit * 2 / 3 : upper_limit * 3 / 2, -1, -1, -1);
       if (err != MDBX_SUCCESS && err != MDBX_UNABLE_EXTEND_MAPSIZE &&
-          err != MDBX_MAP_FULL && err != MDBX_TOO_LARGE &&
-          err != MDBX_RESULT_TRUE)
+          err != MDBX_MAP_FULL && err != MDBX_TOO_LARGE && err != MDBX_EPERM)
         failure_perror("mdbx_env_set_geometry-2", err);
     }
 
@@ -144,8 +142,7 @@ bool testcase_jitter::run() {
       err = mdbx_env_set_geometry(db_guard.get(), -1, -1, upper_limit, -1, -1,
                                   -1);
       if (err != MDBX_SUCCESS && err != MDBX_UNABLE_EXTEND_MAPSIZE &&
-          err != MDBX_MAP_FULL && err != MDBX_TOO_LARGE &&
-          err != MDBX_RESULT_TRUE)
+          err != MDBX_MAP_FULL && err != MDBX_TOO_LARGE && err != MDBX_EPERM)
         failure_perror("mdbx_env_set_geometry-3", err);
     }