diff --git a/src/search.cpp b/src/search.cpp
index a712ce87..46c95ef0 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -625,6 +625,8 @@ namespace {
         if (alpha >= beta)
             return alpha;
     }
+    else
+        thisThread->rootDelta = beta - alpha;
 
     assert(0 <= ss->ply && ss->ply < MAX_PLY);
 
@@ -1167,6 +1169,10 @@ moves_loop: // When in check, search starts here
               && bestMoveCount <= 3)
               r--;
 
+          // Increases reduction for PvNodes that have small window
+          if (PvNode && beta - alpha < thisThread->rootDelta / 4)
+              r++;
+
           // Decrease reduction if position is or has been on the PV
           // and node is not likely to fail low. (~3 Elo)
           if (   ss->ttPv
diff --git a/src/thread.h b/src/thread.h
index e04d303a..fae866c4 100644
--- a/src/thread.h
+++ b/src/thread.h
@@ -72,6 +72,7 @@ public:
   StateInfo rootState;
   Search::RootMoves rootMoves;
   Depth rootDepth, completedDepth;
+  Value rootDelta;
   CounterMoveHistory counterMoves;
   ButterflyHistory mainHistory;
   LowPlyHistory lowPlyHistory;