diff --git a/src/mdbx.c b/src/mdbx.c
index 25b2656b..3445d67f 100644
--- a/src/mdbx.c
+++ b/src/mdbx.c
@@ -4371,6 +4371,13 @@ LIBMDBX_API int mdbx_env_set_geometry(MDBX_env *env, intptr_t size_lower,
   const bool outside_txn =
       (!env->me_txn0 || env->me_txn0->mt_owner != mdbx_thread_self());
 
+#if MDBX_DEBUG
+  if (growth_step < 0)
+    growth_step = 1;
+  if (shrink_threshold < 0)
+    shrink_threshold = 1;
+#endif
+
   int rc = MDBX_PROBLEM;
   if (env->me_map) {
     /* env already mapped */