diff --git a/src/common/bitfield_util.cc b/src/common/bitfield_util.cc
index 8cbe73c8908..bd8a549fd56 100644
--- a/src/common/bitfield_util.cc
+++ b/src/common/bitfield_util.cc
@@ -35,6 +35,7 @@ static uint64_t WrappedSignedBitfieldPlus(uint64_t value, int64_t incr, uint8_t
   return res;
 }
 
+// See also https://github.com/redis/redis/blob/7f4bae817614988c43c3024402d16edcbf3b3277/src/bitops.c#L325
 StatusOr<bool> SignedBitfieldPlus(uint64_t value, int64_t incr, uint8_t bits, BitfieldOverflowBehavior overflow,
                                   uint64_t *dst) {
   Status bits_status(BitfieldEncoding::CheckSupportedBitLengths(BitfieldEncoding::Type::kSigned, bits));
@@ -84,7 +85,7 @@ static uint64_t WrappedUnsignedBitfieldPlus(uint64_t value, int64_t incr, uint8_
   return res;
 }
 
-// return true if overflow.
+// See also https://github.com/redis/redis/blob/7f4bae817614988c43c3024402d16edcbf3b3277/src/bitops.c#L288
 StatusOr<bool> UnsignedBitfieldPlus(uint64_t value, int64_t incr, uint8_t bits, BitfieldOverflowBehavior overflow,
                                     uint64_t *dst) {
   Status bits_status(BitfieldEncoding::CheckSupportedBitLengths(BitfieldEncoding::Type::kUnsigned, bits));
diff --git a/src/common/bitfield_util.h b/src/common/bitfield_util.h
index 08afb18204d..dbb44b1db76 100644
--- a/src/common/bitfield_util.h
+++ b/src/common/bitfield_util.h
@@ -243,7 +243,7 @@ class ArrayBitfieldBitmap {
 
     // for a bits of k signed number, 1 << (bits - 1) is the MSB (most-significant bit).
     // the number is a negative when the MSB is "1".
-    auto msb = static_cast<uint64_t>(1) << (bits - 1);
+    auto msb = static_cast<uint64_t>(1) << (bits - 1);  // NOLINT
     if ((value & msb) != 0) {
       // The way of enlarge width of a signed integer is sign-extended.
       // The values of higher bits should all "1", when the number is negative.