diff --git a/core/src/main/java/org/bitcoinj/core/Transaction.java b/core/src/main/java/org/bitcoinj/core/Transaction.java
index bd1e777b..66c45327 100644
--- a/core/src/main/java/org/bitcoinj/core/Transaction.java
+++ b/core/src/main/java/org/bitcoinj/core/Transaction.java
@@ -35,11 +35,9 @@ import java.io.*;
 import java.util.*;
 
 import static org.bitcoinj.core.Utils.*;
+import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkState;
 import java.math.BigInteger;
-import java.nio.ByteBuffer;
-import java.nio.ByteOrder;
-import org.bitcoinj.script.ScriptChunk;
 
 /**
  * <p>A transaction represents the movement of coins from some addresses to some other addresses. It can also represent
@@ -1203,8 +1201,8 @@ public class Transaction extends ChildMessage {
      */
     public void checkCoinBaseHeight(final int height)
             throws VerificationException {
-        assert height >= Block.BLOCK_HEIGHT_GENESIS;
-        assert isCoinBase();
+        checkArgument(height >= Block.BLOCK_HEIGHT_GENESIS);
+        checkState(isCoinBase());
 
         // Check block height is in coinbase input script
         final TransactionInput in = this.getInputs().get(0);
diff --git a/core/src/main/java/org/bitcoinj/crypto/HDKeyDerivation.java b/core/src/main/java/org/bitcoinj/crypto/HDKeyDerivation.java
index 3dc60a69..78018708 100644
--- a/core/src/main/java/org/bitcoinj/crypto/HDKeyDerivation.java
+++ b/core/src/main/java/org/bitcoinj/crypto/HDKeyDerivation.java
@@ -150,7 +150,7 @@ public final class HDKeyDerivation {
                                                               ChildNumber childNumber) throws HDDerivationException {
         checkArgument(parent.hasPrivKey(), "Parent key must have private key bytes for this method.");
         byte[] parentPublicKey = parent.getPubKeyPoint().getEncoded(true);
-        assert parentPublicKey.length == 33 : parentPublicKey.length;
+        checkState(parentPublicKey.length == 33, "Parent pubkey must be 33 bytes, but is " + parentPublicKey.length);
         ByteBuffer data = ByteBuffer.allocate(37);
         if (childNumber.isHardened()) {
             data.put(parent.getPrivKeyBytes33());
@@ -159,7 +159,7 @@ public final class HDKeyDerivation {
         }
         data.putInt(childNumber.i());
         byte[] i = HDUtils.hmacSha512(parent.getChainCode(), data.array());
-        assert i.length == 64 : i.length;
+        checkState(i.length == 64, i.length);
         byte[] il = Arrays.copyOfRange(i, 0, 32);
         byte[] chainCode = Arrays.copyOfRange(i, 32, 64);
         BigInteger ilInt = new BigInteger(1, il);
@@ -178,12 +178,12 @@ public final class HDKeyDerivation {
     public static RawKeyBytes deriveChildKeyBytesFromPublic(DeterministicKey parent, ChildNumber childNumber, PublicDeriveMode mode) throws HDDerivationException {
         checkArgument(!childNumber.isHardened(), "Can't use private derivation with public keys only.");
         byte[] parentPublicKey = parent.getPubKeyPoint().getEncoded(true);
-        assert parentPublicKey.length == 33 : parentPublicKey.length;
+        checkState(parentPublicKey.length == 33, "Parent pubkey must be 33 bytes, but is " + parentPublicKey.length);
         ByteBuffer data = ByteBuffer.allocate(37);
         data.put(parentPublicKey);
         data.putInt(childNumber.i());
         byte[] i = HDUtils.hmacSha512(parent.getChainCode(), data.array());
-        assert i.length == 64 : i.length;
+        checkState(i.length == 64, i.length);
         byte[] il = Arrays.copyOfRange(i, 0, 32);
         byte[] chainCode = Arrays.copyOfRange(i, 32, 64);
         BigInteger ilInt = new BigInteger(1, il);
diff --git a/core/src/main/java/org/bitcoinj/utils/BtcFormat.java b/core/src/main/java/org/bitcoinj/utils/BtcFormat.java
index 2ef46c87..a8d2bbfd 100644
--- a/core/src/main/java/org/bitcoinj/utils/BtcFormat.java
+++ b/core/src/main/java/org/bitcoinj/utils/BtcFormat.java
@@ -23,6 +23,7 @@ import org.bitcoinj.core.Coin;
 import com.google.common.base.Objects;
 import com.google.common.collect.ImmutableList;
 import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkState;
 import com.google.common.base.Strings;
 
 import java.math.BigDecimal;
@@ -1359,7 +1360,7 @@ public abstract class BtcFormat extends Format {
       * forget to put the symbols back otherwise equals(), hashCode() and immutability will
       * break.  */
     private static DecimalFormatSymbols setSymbolAndCode(DecimalFormat numberFormat, String symbol, String code) {
-        assert Thread.holdsLock(numberFormat);
+        checkState(Thread.holdsLock(numberFormat));
         DecimalFormatSymbols fs = numberFormat.getDecimalFormatSymbols();
         DecimalFormatSymbols ante = (DecimalFormatSymbols)fs.clone();
         fs.setInternationalCurrencySymbol(code);
@@ -1380,7 +1381,7 @@ public abstract class BtcFormat extends Format {
      * @return The DecimalFormatSymbols before changing
      */
     protected static void prefixUnitsIndicator(DecimalFormat numberFormat, int scale) {
-        assert Thread.holdsLock(numberFormat); // make sure caller intends to reset before changing
+        checkState(Thread.holdsLock(numberFormat)); // make sure caller intends to reset before changing
         DecimalFormatSymbols fs = numberFormat.getDecimalFormatSymbols();
         setSymbolAndCode(numberFormat,
             prefixSymbol(fs.getCurrencySymbol(), scale), prefixCode(fs.getInternationalCurrencySymbol(), scale)