diff --git a/fixtures/valid_notation_tests.json b/fixtures/valid_notation_tests.json
index 2daa2ae..a1487dd 100644
--- a/fixtures/valid_notation_tests.json
+++ b/fixtures/valid_notation_tests.json
@@ -17,7 +17,7 @@
 	},
 	{
 		"pos1" : "r2qk2r/pp1n1ppp/2pbpn2/3p4/2PP4/1PNQPN2/P4PPP/R1B1K2R w KQkq - 1 9",
-		"pos2" : "r2qk2r/pp1n1ppp/2pbpn2/3p4/2PP4/1PNQPN2/P4PPP/R1B2RK1 b kq - 0 9",
+		"pos2" : "r2qk2r/pp1n1ppp/2pbpn2/3p4/2PP4/1PNQPN2/P4PPP/R1B2RK1 b kq - 2 9",
 		"algText" : "O-O",
 		"longAlgText" : "O-O",
 		"uciText" : "e1g1",
@@ -73,7 +73,7 @@
 	},
 	{
 		"pos1" : "rnbk1b1r/p3pppp/5n2/2p1p3/5B2/2N2P2/PPP3PP/R3KBNR w KQ - 0 10",
-		"pos2" : "rnbk1b1r/p3pppp/5n2/2p1p3/5B2/2N2P2/PPP3PP/2KR1BNR b - - 0 10",
+		"pos2" : "rnbk1b1r/p3pppp/5n2/2p1p3/5B2/2N2P2/PPP3PP/2KR1BNR b - - 1 10",
 		"algText" : "O-O-O+",
 		"longAlgText" : "O-O-O+",
 		"uciText" : "e1c1",
diff --git a/move_test.go b/move_test.go
index ceccb99..bde6b37 100644
--- a/move_test.go
+++ b/move_test.go
@@ -133,7 +133,7 @@ var (
 		{
 			m:       &Move{s1: E1, s2: G1, tags: KingSideCastle},
 			pos:     unsafeFEN("r3k2r/8/8/8/8/8/8/R3K2R w KQkq - 0 1"),
-			postPos: unsafeFEN("r3k2r/8/8/8/8/8/8/R4RK1 b kq - 0 1"),
+			postPos: unsafeFEN("r3k2r/8/8/8/8/8/8/R4RK1 b kq - 1 1"),
 		},
 		{
 			m:       &Move{s1: A4, s2: B3, tags: EnPassant},
@@ -143,7 +143,49 @@ var (
 		{
 			m:       &Move{s1: E1, s2: G1, tags: KingSideCastle},
 			pos:     unsafeFEN("r2qk2r/pp1n1ppp/2pbpn2/3p4/2PP4/1PNQPN2/P4PPP/R1B1K2R w KQkq - 1 9"),
-			postPos: unsafeFEN("r2qk2r/pp1n1ppp/2pbpn2/3p4/2PP4/1PNQPN2/P4PPP/R1B2RK1 b kq - 0 9"),
+			postPos: unsafeFEN("r2qk2r/pp1n1ppp/2pbpn2/3p4/2PP4/1PNQPN2/P4PPP/R1B2RK1 b kq - 2 9"),
+		},
+		// half move clock - knight move to f3 from starting position
+		{
+			m:       &Move{s1: G1, s2: F3},
+			pos:     unsafeFEN("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"),
+			postPos: unsafeFEN("rnbqkbnr/pppppppp/8/8/8/5N2/PPPPPPPP/RNBQKB1R b KQkq - 1 1"),
+		},
+		// half move clock - king side castle
+		{
+			m:       &Move{s1: E1, s2: G1, tags: KingSideCastle},
+			pos:     unsafeFEN("r3k2r/8/8/8/8/8/8/R3K2R w KQkq - 0 1"),
+			postPos: unsafeFEN("r3k2r/8/8/8/8/8/8/R4RK1 b kq - 1 1"),
+		},
+		// half move clock - queen side castle
+		{
+			m:       &Move{s1: E1, s2: C1, tags: QueenSideCastle},
+			pos:     unsafeFEN("r3k2r/ppqn1ppp/2pbpn2/3p4/2PP4/1PNQPN2/P2B1PPP/R3K2R w KQkq - 3 10"),
+			postPos: unsafeFEN("r3k2r/ppqn1ppp/2pbpn2/3p4/2PP4/1PNQPN2/P2B1PPP/2KR3R b kq - 4 10"),
+		},
+		// half move clock - pawn push
+		{
+			m:       &Move{s1: E2, s2: E4},
+			pos:     unsafeFEN("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"),
+			postPos: unsafeFEN("rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1"),
+		},
+		// half move clock - pawn capture
+		{
+			m:       &Move{s1: E4, s2: D5, tags: Capture},
+			pos:     unsafeFEN("r1bqkbnr/ppp1pppp/2n5/3p4/4P3/5N2/PPPP1PPP/RNBQKB1R w KQkq - 2 3"),
+			postPos: unsafeFEN("r1bqkbnr/ppp1pppp/2n5/3P4/8/5N2/PPPP1PPP/RNBQKB1R b KQkq - 0 3"),
+		},
+		// half move clock - en passant
+		{
+			m:       &Move{s1: E5, s2: F6, tags: EnPassant},
+			pos:     unsafeFEN("r1bqkbnr/ppp1p1pp/2n5/3pPp2/8/5N2/PPPP1PPP/RNBQKB1R w KQkq f6 0 4"),
+			postPos: unsafeFEN("r1bqkbnr/ppp1p1pp/2n2P2/3p4/8/5N2/PPPP1PPP/RNBQKB1R b KQkq - 0 4"),
+		},
+		// half move clock - piece captured by knight
+		{
+			m:       &Move{s1: C6, s2: D4, tags: Capture},
+			pos:     unsafeFEN("r1bqkbnr/ppp1p1pp/2n5/3pPp2/3N4/8/PPPP1PPP/RNBQKB1R b KQkq - 1 4"),
+			postPos: unsafeFEN("r1bqkbnr/ppp1p1pp/8/3pPp2/3n4/8/PPPP1PPP/RNBQKB1R w KQkq - 0 5"),
 		},
 	}
 )
diff --git a/notation_test.go b/notation_test.go
index c005904..d528a4f 100644
--- a/notation_test.go
+++ b/notation_test.go
@@ -51,7 +51,8 @@ func TestValidDecoding(t *testing.T) {
 			}
 			postPos := test.Pos1.Update(m)
 			if test.Pos2.String() != postPos.String() {
-				t.Fatalf("starting from board \n%s\n after move %s\n expected board to be %s\n%s\n but was %s\n%s\n",
+				t.Fatalf("starting from board \n%s%s\n after move %s\n expected board to be %s\n%s\n but was %s\n%s\n",
+					test.Pos1.String(),
 					test.Pos1.board.Draw(), m.String(), test.Pos2.String(),
 					test.Pos2.board.Draw(), postPos.String(), postPos.board.Draw())
 			}
@@ -86,7 +87,7 @@ var (
 			N:       AlgebraicNotation{},
 			Pos:     unsafeFEN("r2qk2r/pp1n1ppp/2pbpn2/3p4/2PP4/1PNQPN2/P4PPP/R1B1K2R w KQkq - 1 9"),
 			Text:    "O-O-O-O",
-			PostPos: unsafeFEN("r2qk2r/pp1n1ppp/2pbpn2/3p4/2PP4/1PNQPN2/P4PPP/R1B2RK1 b kq - 0 9"),
+			PostPos: unsafeFEN("r2qk2r/pp1n1ppp/2pbpn2/3p4/2PP4/1PNQPN2/P4PPP/R1B2RK1 b kq - 2 9"),
 		},
 		{
 			// http://en.lichess.org/W91M4jms#23
diff --git a/position.go b/position.go
index ad3548c..ee67fa9 100644
--- a/position.go
+++ b/position.go
@@ -74,11 +74,10 @@ func (pos *Position) Update(m *Move) *Position {
 	if pos.turn == Black {
 		moveCount++
 	}
-	cr := pos.CastleRights()
 	ncr := pos.updateCastleRights(m)
 	p := pos.board.Piece(m.s1)
 	halfMove := pos.halfMoveClock
-	if p.Type() == Pawn || m.HasTag(Capture) || cr != ncr {
+	if p.Type() == Pawn || m.HasTag(Capture) {
 		halfMove = 0
 	} else {
 		halfMove++