1 files changed, 17 insertions, 6 deletions
diff --git a/src/dynamic.c b/src/dynamic.c
index c6e86e3..694fe50 100755
--- a/src/dynamic.c
+++ b/src/dynamic.c
@@ -289,10 +289,21 @@ Return value:
         {
             ctx->mvKillerEscapes[uPly][1] = ctx->mvKillerEscapes[uPly][0];
             ctx->mvKillerEscapes[uPly][0] = mv;
-            if (ctx->mvKillerEscapes[uPly][1].uMove == 0)
-            {
-                ctx->mvKillerEscapes[uPly][1] = ctx->mvNullmoveRefutations[uPly];
-            }
+            // No mvNullmoveQuietRefutations backfill here, unlike the
+            // regular killer table below: TryNullmovePruning asserts
+            // !InCheck() before probing, and a null move doesn't move
+            // any piece, so the move that refutes it is necessarily
+            // played from a position where the opponent was *not* in
+            // check either -- it can never legitimately be a check
+            // evasion. Backfilling with it here wouldn't be dead code
+            // the way the old capture-into-quiet-slot bug was (that
+            // was mathematically guaranteed to never match); since
+            // IS_SAME_MOVE ignores bvFlags, an ordinary quiet move
+            // from some unrelated non-check position could coincide
+            // with a real escaping candidate by cFrom/cTo/pMoved/
+            // pCaptured/pPromoted alone and pick up an undeserved
+            // SECOND_KILLER bonus in evasion ordering. Leave the slot
+            // empty instead of risking that.
         }
         ASSERT(!IS_SAME_MOVE(ctx->mvKillerEscapes[uPly][0],
                              ctx->mvKillerEscapes[uPly][1]));
@@ -304,9 +315,9 @@ Return value:
         {
             ctx->mvKiller[uPly][1] = ctx->mvKiller[uPly][0];
             ctx->mvKiller[uPly][0] = mv;
-            if (ctx->mvKiller[uPly][1].uMove == 0) 
+            if (ctx->mvKiller[uPly][1].uMove == 0)
             {
-                ctx->mvKiller[uPly][1] = ctx->mvNullmoveRefutations[uPly];
+                ctx->mvKiller[uPly][1] = ctx->mvNullmoveQuietRefutations[uPly];
             }
         }
         ASSERT(!IS_SAME_MOVE(ctx->mvKiller[uPly][0], ctx->mvKiller[uPly][1]));