diff --git a/grin/src/server.rs b/grin/src/server.rs
index c3e5a91d..33faa556 100644
--- a/grin/src/server.rs
+++ b/grin/src/server.rs
@@ -322,8 +322,8 @@ impl Server {
 			DiffStats {
 				height: tip_height as u64,
 				last_blocks: diff_entries,
-				average_block_time: block_time_sum / consensus::DIFFICULTY_ADJUST_WINDOW,
-				average_difficulty: block_diff_sum / consensus::DIFFICULTY_ADJUST_WINDOW,
+				average_block_time: block_time_sum / (consensus::DIFFICULTY_ADJUST_WINDOW - 1),
+				average_difficulty: block_diff_sum / (consensus::DIFFICULTY_ADJUST_WINDOW - 1),
 				window_size: consensus::DIFFICULTY_ADJUST_WINDOW,
 			}
 		};