diff --git a/triedb/pathdb/history_index_block.go b/triedb/pathdb/history_index_block.go
index 0b2f44b7d3..fd43d81b78 100644
--- a/triedb/pathdb/history_index_block.go
+++ b/triedb/pathdb/history_index_block.go
@@ -28,7 +28,7 @@ import (
 
 const (
 	indexBlockDescSize   = 14   // The size of index block descriptor
-	indexBlockSizeCap    = 4096 // The maximum size of a single index block
+	indexBlockMaxSize    = 4096 // The maximum size of a single index block
 	indexBlockRestartLen = 256  // The restart interval length of index block
 )
 
@@ -457,7 +457,7 @@ func (b *blockWriter) empty() bool {
 
 func (b *blockWriter) estimateFull(ext []uint16) bool {
 	size := 8 + 2*len(ext)
-	return len(b.data)+size > indexBlockSizeCap
+	return len(b.data)+size > indexBlockMaxSize
 }
 
 // last returns the last element in the block. It should only be called when
diff --git a/triedb/pathdb/history_index_iterator.go b/triedb/pathdb/history_index_iterator.go
index 8731687c5e..076baaa9e5 100644
--- a/triedb/pathdb/history_index_iterator.go
+++ b/triedb/pathdb/history_index_iterator.go
@@ -126,7 +126,7 @@ func (f extFilter) contains(bitmap []byte) (bool, error) {
 			}
 			// Check descendants: the presence of any descendant implicitly
 			// represents a mutation of its ancestor.
-			return isByteSet(bitmap, 2+2*n) || isByteSet(bitmap, 3+2*n), nil
+			return bitmap[2+2*n] != 0 || bitmap[3+2*n] != 0, nil
 		}
 	default:
 		return false, fmt.Errorf("unsupported bitmap size %d", len(bitmap))
diff --git a/triedb/pathdb/history_trienode.go b/triedb/pathdb/history_trienode.go
index 360d248aa0..6c0c0fe8cc 100644
--- a/triedb/pathdb/history_trienode.go
+++ b/triedb/pathdb/history_trienode.go
@@ -208,7 +208,7 @@ func (h *trienodeHistory) encode() ([]byte, []byte, []byte, error) {
 				restarts = append(restarts, internalValOffset)
 				prefixLen = 0
 			} else {
-				prefixLen = sharedLen(prevKey, key)
+				prefixLen = commonPrefixLen(prevKey, key)
 			}
 			value := h.nodes[owner][path]
 
diff --git a/triedb/pathdb/history_trienode_test.go b/triedb/pathdb/history_trienode_test.go
index be4740a904..0c0422f00f 100644
--- a/triedb/pathdb/history_trienode_test.go
+++ b/triedb/pathdb/history_trienode_test.go
@@ -580,8 +580,8 @@ func TestTrienodeHistoryReaderIterator(t *testing.T) {
 	}
 }
 
-// TestSharedLen tests the sharedLen helper function
-func TestSharedLen(t *testing.T) {
+// TestCommonPrefixLen tests the commonPrefixLen helper function
+func TestCommonPrefixLen(t *testing.T) {
 	tests := []struct {
 		a, b     []byte
 		expected int
@@ -610,13 +610,13 @@ func TestSharedLen(t *testing.T) {
 	}
 
 	for i, test := range tests {
-		result := sharedLen(test.a, test.b)
+		result := commonPrefixLen(test.a, test.b)
 		if result != test.expected {
 			t.Errorf("Test %d: sharedLen(%q, %q) = %d, expected %d",
 				i, test.a, test.b, result, test.expected)
 		}
 		// Test commutativity
-		resultReverse := sharedLen(test.b, test.a)
+		resultReverse := commonPrefixLen(test.b, test.a)
 		if result != resultReverse {
 			t.Errorf("Test %d: sharedLen is not commutative: sharedLen(a,b)=%d, sharedLen(b,a)=%d",
 				i, result, resultReverse)
diff --git a/triedb/pathdb/history_trienode_utils.go b/triedb/pathdb/history_trienode_utils.go
index b30373cf24..0513343404 100644
--- a/triedb/pathdb/history_trienode_utils.go
+++ b/triedb/pathdb/history_trienode_utils.go
@@ -22,8 +22,8 @@ import (
 	"slices"
 )
 
-// sharedLen returns the length of the common prefix shared by a and b.
-func sharedLen(a, b []byte) int {
+// commonPrefixLen returns the length of the common prefix shared by a and b.
+func commonPrefixLen(a, b []byte) int {
 	n := min(len(a), len(b))
 	for i := range n {
 		if a[i] != b[i] {
@@ -74,15 +74,10 @@ func isAncestor(x, y uint16) bool {
 
 // isBitSet reports whether the bit at `index` in the byte slice `b` is set.
 func isBitSet(b []byte, index int) bool {
-	return b[index/8]&(1<<(index%8)) != 0
-}
-
-// isByteSet reports whether the byte at `index` in the byte slice `b` is set.
-func isByteSet(b []byte, index int) bool {
-	return b[index] != 0
+	return b[index/8]&(1<<(7-index%8)) != 0
 }
 
 // setBit sets the bit at `index` in the byte slice `b` to 1.
 func setBit(b []byte, index int) {
-	b[index/8] |= 1 << (index % 8)
+	b[index/8] |= 1 << (7 - index%8)
 }
diff --git a/triedb/pathdb/history_trienode_utils_test.go b/triedb/pathdb/history_trienode_utils_test.go
index 23efb65d14..17eabb2a98 100644
--- a/triedb/pathdb/history_trienode_utils_test.go
+++ b/triedb/pathdb/history_trienode_utils_test.go
@@ -17,6 +17,7 @@
 package pathdb
 
 import (
+	"bytes"
 	"testing"
 )
 
@@ -44,3 +45,37 @@ func TestIsAncestor(t *testing.T) {
 		}
 	}
 }
+
+func TestBitmapSet(t *testing.T) {
+	suites := []struct {
+		index  int
+		expect []byte
+	}{
+		{
+			0, []byte{0b10000000, 0x0},
+		},
+		{
+			1, []byte{0b01000000, 0x0},
+		},
+		{
+			7, []byte{0b00000001, 0x0},
+		},
+		{
+			8, []byte{0b00000000, 0b10000000},
+		},
+		{
+			15, []byte{0b00000000, 0b00000001},
+		},
+	}
+	for _, tc := range suites {
+		var buf [2]byte
+		setBit(buf[:], tc.index)
+
+		if !bytes.Equal(buf[:], tc.expect) {
+			t.Fatalf("bitmap = %v, want %v", buf, tc.expect)
+		}
+		if !isBitSet(buf[:], tc.index) {
+			t.Fatal("bit is not set")
+		}
+	}
+}