diff --git a/drama/src/rev-mc.c b/drama/src/rev-mc.c
index 96b8f1f..27d7bb4 100644
--- a/drama/src/rev-mc.c
+++ b/drama/src/rev-mc.c
@@ -375,7 +375,7 @@ find_row_mask(std::vector<set_t> &sets,
                     if (my_end_pos > g_base_pos.load(std::memory_order_relaxed) + step_count) {
                         std::lock_guard<std::mutex> _(lock);
                         if (my_end_pos > g_base_pos + step_count) {
-                            g_base_pos = my_end_pos;
+                            g_base_pos = my_end_pos - step_count;
                             row_mask   = cur_mask;
                         }
                     } else if (g_base_pos.load(std::memory_order_relaxed) <= my_end_pos) {