diff --git a/moves_io.cpp b/moves_io.cpp
index fe3f952..49acb17 100644
--- a/moves_io.cpp
+++ b/moves_io.cpp
@@ -92,16 +92,18 @@ template <typename T, typename V> Move uciToMove(const _Position<T, V> &pos, std
 
     // promotion
     if (pt == PAWN && uci.length() == 5 && (rank_of(target) == (pos.sideToMove() == WHITE ? RANK_8 : RANK_1))) {
-        auto promotion = parse_pt(uci.substr(4, 1));
+        auto promotion = parse_pt(uci[4]);
 
         if (promotion == NO_PIECE_TYPE || promotion == KING || promotion == PAWN) {
-#ifdef __EXCEPTIONS
+#if defined(_DEBUG) || !defined(NDEBUG)
+            assert(false && "promotions: NRBQ");
+#elif defined(__EXCEPTIONS) && (defined(_DEBUG) || !defined(NDEBUG))
             throw std::invalid_argument("promotions: NRBQ");
 #endif
             return Move::NO_MOVE;
         }
 
-        return Move::make<PROMOTION>(source, target, parse_pt(uci.substr(4, 1)));
+        return Move::make<PROMOTION>(source, target, promotion);
     }
     auto move = (uci.length() == 4) ? Move::make(source, target) : Move::NO_MOVE;
     Movelist moves;
@@ -124,4 +126,4 @@ INSTANTITATE(ContiguousMappingPiece)
 #undef INSTANTITATE
 } // namespace uci
 std::string Move::uci() const { return uci::moveToUci(*this); }
-} // namespace chess
\ No newline at end of file
+} // namespace chess
diff --git a/types.h b/types.h
index 3579972..6818203 100644
--- a/types.h
+++ b/types.h
@@ -337,14 +337,17 @@ template <typename T, std::size_t MaxSize> class ValueList {
 using Movelist = ValueList<Move, 256>;
 constexpr int square_distance(Square a, Square b) { return std::max(std::abs(file_of(a) - file_of(b)), std::abs(rank_of(a) - rank_of(b))); }
 constexpr Square parse_square(std::string_view sv) { return make_sq(File(sv[0] - 'a'), Rank(sv[1] - '1')); }
-constexpr PieceType parse_pt(std::string_view sv) {
+constexpr PieceType parse_pt(unsigned char c) {
     const char a[] = "pnbrqk";
-    int p = 0;
+    int p = -1;
+    (c >='A' && c<='Z') ? (c += 32) : (c); // tolower
     for (size_t i = 0; i < sizeof(a); i++) {
-        if (sv[0] == a[i])
+        if (c == a[i])
             p = i;
     }
     return static_cast<PieceType>(p + 1);
 }
 
 } // namespace chess
+
+