diff --git a/src/eval/nnue/features/half_kp.cpp b/src/eval/nnue/features/half_kp.cpp
index 1741f3ce..5cd95637 100644
--- a/src/eval/nnue/features/half_kp.cpp
+++ b/src/eval/nnue/features/half_kp.cpp
@@ -42,7 +42,9 @@ void HalfKP<AssociatedKing>::AppendActiveIndices(
   Square sq_target_k;
   GetPieces(pos, perspective, &pieces, &sq_target_k);
   for (PieceNumber i = PIECE_NUMBER_ZERO; i < PIECE_NUMBER_KING; ++i) {
-    active->push_back(MakeIndex(sq_target_k, pieces[i]));
+    if (pieces[i] != Eval::BONA_PIECE_ZERO) {
+      active->push_back(MakeIndex(sq_target_k, pieces[i]));
+    }
   }
 }
 
@@ -59,10 +61,14 @@ void HalfKP<AssociatedKing>::AppendChangedIndices(
     if (dp.pieceNo[i] >= PIECE_NUMBER_KING) continue;
     const auto old_p = static_cast<BonaPiece>(
         dp.changed_piece[i].old_piece.from[perspective]);
-    removed->push_back(MakeIndex(sq_target_k, old_p));
+    if (old_p != Eval::BONA_PIECE_ZERO) {
+      removed->push_back(MakeIndex(sq_target_k, old_p));
+    }
     const auto new_p = static_cast<BonaPiece>(
         dp.changed_piece[i].new_piece.from[perspective]);
-    added->push_back(MakeIndex(sq_target_k, new_p));
+    if (new_p != Eval::BONA_PIECE_ZERO) {
+      added->push_back(MakeIndex(sq_target_k, new_p));
+    }
   }
 }
 
diff --git a/src/eval/nnue/features/half_relative_kp.cpp b/src/eval/nnue/features/half_relative_kp.cpp
index d0810df6..d62beea0 100644
--- a/src/eval/nnue/features/half_relative_kp.cpp
+++ b/src/eval/nnue/features/half_relative_kp.cpp
@@ -50,7 +50,9 @@ void HalfRelativeKP<AssociatedKing>::AppendActiveIndices(
   GetPieces(pos, perspective, &pieces, &sq_target_k);
   for (PieceNumber i = PIECE_NUMBER_ZERO; i < PIECE_NUMBER_KING; ++i) {
     if (pieces[i] >= fe_hand_end) {
-      active->push_back(MakeIndex(sq_target_k, pieces[i]));
+      if (pieces[i] != Eval::BONA_PIECE_ZERO) {
+        active->push_back(MakeIndex(sq_target_k, pieces[i]));
+      }
     }
   }
 }
@@ -69,12 +71,16 @@ void HalfRelativeKP<AssociatedKing>::AppendChangedIndices(
     const auto old_p = static_cast<BonaPiece>(
         dp.changed_piece[i].old_piece.from[perspective]);
     if (old_p >= fe_hand_end) {
-      removed->push_back(MakeIndex(sq_target_k, old_p));
+      if (old_p != Eval::BONA_PIECE_ZERO) {
+        removed->push_back(MakeIndex(sq_target_k, old_p));
+      }
     }
     const auto new_p = static_cast<BonaPiece>(
         dp.changed_piece[i].new_piece.from[perspective]);
     if (new_p >= fe_hand_end) {
-      added->push_back(MakeIndex(sq_target_k, new_p));
+      if (new_p != Eval::BONA_PIECE_ZERO) {
+        added->push_back(MakeIndex(sq_target_k, new_p));
+      }
     }
   }
 }
diff --git a/src/eval/nnue/features/p.cpp b/src/eval/nnue/features/p.cpp
index da1481cb..56bca0a4 100644
--- a/src/eval/nnue/features/p.cpp
+++ b/src/eval/nnue/features/p.cpp
@@ -21,7 +21,9 @@ void P::AppendActiveIndices(
       pos.eval_list()->piece_list_fb() :
       pos.eval_list()->piece_list_fw();
   for (PieceNumber i = PIECE_NUMBER_ZERO; i < PIECE_NUMBER_KING; ++i) {
-    active->push_back(pieces[i]);
+    if (pieces[i] != Eval::BONA_PIECE_ZERO) {
+      active->push_back(pieces[i]);
+    }
   }
 }
 
@@ -32,8 +34,12 @@ void P::AppendChangedIndices(
   const auto& dp = pos.state()->dirtyPiece;
   for (int i = 0; i < dp.dirty_num; ++i) {
     if (dp.pieceNo[i] >= PIECE_NUMBER_KING) continue;
-    removed->push_back(dp.changed_piece[i].old_piece.from[perspective]);
-    added->push_back(dp.changed_piece[i].new_piece.from[perspective]);
+    if (dp.changed_piece[i].old_piece.from[perspective] != Eval::BONA_PIECE_ZERO) {
+      removed->push_back(dp.changed_piece[i].old_piece.from[perspective]);
+    }
+    if (dp.changed_piece[i].new_piece.from[perspective] != Eval::BONA_PIECE_ZERO) {
+      added->push_back(dp.changed_piece[i].new_piece.from[perspective]);
+    }
   }
 }