diff --git a/src/main/java/com/sparrowwallet/drongo/protocol/Transaction.java b/src/main/java/com/sparrowwallet/drongo/protocol/Transaction.java
index 7445aed..d999d86 100644
--- a/src/main/java/com/sparrowwallet/drongo/protocol/Transaction.java
+++ b/src/main/java/com/sparrowwallet/drongo/protocol/Transaction.java
@@ -21,9 +21,10 @@ public class Transaction extends TransactionPart {
     public static final int MAX_BLOCK_SIZE = 1000 * 1000;
     public static final long MAX_BITCOIN = 21 * 1000 * 1000L;
     public static final long SATOSHIS_PER_BITCOIN = 100 * 1000 * 1000L;
+    public static final long MAX_BLOCK_LOCKTIME = 500000000L;
 
     private long version;
-    private long lockTime;
+    private long locktime;
     private boolean segwit;
     private int segwitVersion;
 
@@ -45,19 +46,34 @@ public class Transaction extends TransactionPart {
         this.version = version;
     }
 
-    public long getLockTime() {
-        return lockTime;
+    public long getLocktime() {
+        return locktime;
     }
 
-    public void setLockTime(long lockTime) {
-        this.lockTime = lockTime;
+    public void setLocktime(long locktime) {
+        this.locktime = locktime;
     }
 
-    public boolean isLockTimeEnabled() {
-        if(lockTime == 0) return false;
+    public boolean isLocktimeEnabled() {
+        if(locktime == 0) return false;
+        return isLocktimeSequenceEnabled();
+    }
+
+    public boolean isLocktimeSequenceEnabled() {
+        for(TransactionInput input : inputs) {
+            if(!input.isAbsoluteTimeLockDisabled()) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    public boolean isReplaceByFee() {
+        if(locktime == 0) return false;
 
         for(TransactionInput input : inputs) {
-            if(input.getSequenceNumber() != TransactionInput.SEQUENCE_LOCKTIME_DISABLED) {
+            if(input.isReplaceByFeeEnabled()) {
                 return true;
             }
         }
@@ -149,7 +165,7 @@ public class Transaction extends TransactionPart {
             }
         }
         // lock_time
-        uint32ToByteStreamLE(lockTime, stream);
+        uint32ToByteStreamLE(locktime, stream);
     }
 
     /**
@@ -176,7 +192,7 @@ public class Transaction extends TransactionPart {
         if (segwit)
             parseWitnesses();
         // lock_time
-        lockTime = readUint32();
+        locktime = readUint32();
 
         length = cursor - offset;
     }
@@ -456,7 +472,7 @@ public class Transaction extends TransactionPart {
             uint64ToByteStreamLE(BigInteger.valueOf(prevValue), bos);
             uint32ToByteStreamLE(inputs.get(inputIndex).getSequenceNumber(), bos);
             bos.write(hashOutputs);
-            uint32ToByteStreamLE(this.lockTime, bos);
+            uint32ToByteStreamLE(this.locktime, bos);
             uint32ToByteStreamLE(0x000000ff & sigHashType, bos);
         } catch (IOException e) {
             throw new RuntimeException(e);  // Cannot happen.
diff --git a/src/main/java/com/sparrowwallet/drongo/protocol/TransactionInput.java b/src/main/java/com/sparrowwallet/drongo/protocol/TransactionInput.java
index 040c0b1..9c3f88a 100644
--- a/src/main/java/com/sparrowwallet/drongo/protocol/TransactionInput.java
+++ b/src/main/java/com/sparrowwallet/drongo/protocol/TransactionInput.java
@@ -6,7 +6,10 @@ import java.io.IOException;
 import java.io.OutputStream;
 
 public class TransactionInput extends TransactionPart {
-    public static final long SEQUENCE_LOCKTIME_DISABLED = 0xFFFFFFFF;
+    public static final long SEQUENCE_LOCKTIME_DISABLED = 4294967295L;
+    public static final long SEQUENCE_RBF_ENABLED = 4294967293L;
+    public static final long MAX_RELATIVE_TIMELOCK = 0x40FFFF;
+    public static final long MAX_RELATIVE_TIMELOCK_IN_BLOCKS = 0xFFFF;
 
     // Allows for altering transactions after they were broadcast. Values below NO_SEQUENCE-1 mean it can be altered.
     private long sequence;
@@ -97,6 +100,30 @@ public class TransactionInput extends TransactionPart {
                 (outpoint.getIndex() & 0xFFFFFFFFL) == 0xFFFFFFFFL;  // -1 but all is serialized to the wire as unsigned int.
     }
 
+    public boolean isReplaceByFeeEnabled() {
+        return sequence <= SEQUENCE_RBF_ENABLED;
+    }
+
+    public boolean isAbsoluteTimeLockDisabled() {
+        return sequence >= SEQUENCE_LOCKTIME_DISABLED;
+    }
+
+    public boolean isAbsoluteTimeLocked() {
+        return !isAbsoluteTimeLockDisabled() && !isRelativeTimeLocked();
+    }
+
+    public boolean isRelativeTimeLocked() {
+        return sequence <= MAX_RELATIVE_TIMELOCK;
+    }
+
+    public boolean isRelativeTimeLockedInBlocks() {
+        return sequence <= MAX_RELATIVE_TIMELOCK_IN_BLOCKS;
+    }
+
+    public long getRelativeLocktime() {
+        return sequence & MAX_RELATIVE_TIMELOCK_IN_BLOCKS;
+    }
+
     protected void bitcoinSerializeToStream(OutputStream stream) throws IOException {
         outpoint.bitcoinSerializeToStream(stream);
         stream.write(new VarInt(scriptBytes.length).encode());
diff --git a/src/main/java/com/sparrowwallet/drongo/psbt/PSBT.java b/src/main/java/com/sparrowwallet/drongo/psbt/PSBT.java
index d40bd7d..d207127 100644
--- a/src/main/java/com/sparrowwallet/drongo/psbt/PSBT.java
+++ b/src/main/java/com/sparrowwallet/drongo/psbt/PSBT.java
@@ -202,7 +202,7 @@ public class PSBT {
                     transaction.verify();
                     inputs = transaction.getInputs().size();
                     outputs = transaction.getOutputs().size();
-                    log.debug("Transaction with txid: " + transaction.getTxId() + " version " + transaction.getVersion() + " size " + transaction.getMessageSize() + " locktime " + transaction.getLockTime());
+                    log.debug("Transaction with txid: " + transaction.getTxId() + " version " + transaction.getVersion() + " size " + transaction.getMessageSize() + " locktime " + transaction.getLocktime());
                     for(TransactionInput input: transaction.getInputs()) {
                         if(input.getScriptSig().getProgram().length != 0) {
                             throw new PSBTParseException("Unsigned tx input does not have empty scriptSig");
diff --git a/src/main/java/com/sparrowwallet/drongo/psbt/PSBTInput.java b/src/main/java/com/sparrowwallet/drongo/psbt/PSBTInput.java
index 42a484b..e450df3 100644
--- a/src/main/java/com/sparrowwallet/drongo/psbt/PSBTInput.java
+++ b/src/main/java/com/sparrowwallet/drongo/psbt/PSBTInput.java
@@ -65,7 +65,7 @@ public class PSBTInput {
                     }
 
                     this.nonWitnessUtxo = nonWitnessTx;
-                    log.debug("Found input non witness utxo with txid: " + nonWitnessTx.getTxId() + " version " + nonWitnessTx.getVersion() + " size " + nonWitnessTx.getMessageSize() + " locktime " + nonWitnessTx.getLockTime());
+                    log.debug("Found input non witness utxo with txid: " + nonWitnessTx.getTxId() + " version " + nonWitnessTx.getVersion() + " size " + nonWitnessTx.getMessageSize() + " locktime " + nonWitnessTx.getLocktime());
                     for(TransactionInput input: nonWitnessTx.getInputs()) {
                         log.debug(" Transaction input references txid: " + input.getOutpoint().getHash() + " vout " + input.getOutpoint().getIndex() + " with script " + input.getScriptSig());
                     }