diff --git a/core/src/main/java/com/google/bitcoin/core/Peer.java b/core/src/main/java/com/google/bitcoin/core/Peer.java
index 6d4d9416..d520a1c9 100644
--- a/core/src/main/java/com/google/bitcoin/core/Peer.java
+++ b/core/src/main/java/com/google/bitcoin/core/Peer.java
@@ -47,7 +47,7 @@ public class Peer {
     private static final Logger log = LoggerFactory.getLogger(Peer.class);
 
     private final NetworkParameters params;
-    private final BlockChain blockChain;
+    private final AbstractBlockChain blockChain;
     // When an API user explicitly requests a block or transaction from a peer, the InventoryItem is put here
     // whilst waiting for the response. Synchronized on itself. Is not used for downloads Peer generates itself.
     // TODO: Make this work for transactions as well.
@@ -87,9 +87,9 @@ public class Peer {
     /**
      * Construct a peer that reads/writes from the given block chain.
      */
-    public Peer(NetworkParameters params, BlockChain blockChain, VersionMessage ver) {
+    public Peer(NetworkParameters params, AbstractBlockChain chain2, VersionMessage ver) {
         this.params = params;
-        this.blockChain = blockChain;
+        this.blockChain = chain2;
         this.versionMessage = ver;
         this.pendingGetBlockFutures = new ArrayList<GetDataFuture<Block>>();
         this.eventListeners = new CopyOnWriteArrayList<PeerEventListener>();
@@ -103,7 +103,7 @@ public class Peer {
      * Construct a peer that reads/writes from the given chain. Automatically creates a VersionMessage for you from the
      * given software name/version strings, which should be something like "MySimpleTool", "1.0"
      */
-    public Peer(NetworkParameters params, BlockChain blockChain, String thisSoftwareName, String thisSoftwareVersion) {
+    public Peer(NetworkParameters params, AbstractBlockChain blockChain, String thisSoftwareName, String thisSoftwareVersion) {
         this(params, blockChain, null);
         this.versionMessage = new VersionMessage(params, blockChain.getBestChainHeight());
         this.versionMessage.appendToSubVer(thisSoftwareName, thisSoftwareVersion, null);
diff --git a/core/src/main/java/com/google/bitcoin/core/PeerGroup.java b/core/src/main/java/com/google/bitcoin/core/PeerGroup.java
index ebe00c9d..1789a42b 100644
--- a/core/src/main/java/com/google/bitcoin/core/PeerGroup.java
+++ b/core/src/main/java/com/google/bitcoin/core/PeerGroup.java
@@ -94,6 +94,7 @@ public class PeerGroup {
     private int maxConnections;
 
     private final NetworkParameters params;
+    private final AbstractBlockChain chain;
     private int connectionDelayMillis;
     private long fastCatchupTimeSecs;
     private ArrayList<Wallet> wallets;
@@ -125,10 +126,10 @@ public class PeerGroup {
      * about blocks or pending transactions, you can just provide a MemoryBlockStore and a newly created Wallet.
      *
      * @param params Network parameters
-     * @param chain a BlockChain object that will receive and handle block messages.
+     * @param chain2 a BlockChain object that will receive and handle block messages.
      */
-    public PeerGroup(NetworkParameters params, BlockChain chain) {
-        this(params, chain, DEFAULT_CONNECTION_DELAY_MILLIS);
+    public PeerGroup(NetworkParameters params, AbstractBlockChain chain2) {
+        this(params, chain2, DEFAULT_CONNECTION_DELAY_MILLIS);
     }
 
     /**
@@ -139,7 +140,7 @@ public class PeerGroup {
      * @param connectionDelayMillis how long to wait between attempts to connect to nodes or read
      *                              from any added peer discovery sources
      */
-    public PeerGroup(final NetworkParameters params, final BlockChain chain,
+    public PeerGroup(final NetworkParameters params, final AbstractBlockChain chain,
             int connectionDelayMillis) {
         this(params, chain, connectionDelayMillis, new ClientBootstrap(
                 new NioClientSocketChannelFactory(
@@ -148,9 +149,10 @@ public class PeerGroup {
         bootstrap.setPipelineFactory(makePipelineFactory(params, chain));
     }
 
-    PeerGroup(final NetworkParameters params, final BlockChain chain,
+    PeerGroup(final NetworkParameters params, final AbstractBlockChain chain,
               int connectionDelayMillis, ClientBootstrap bootstrap) {
         this.params = params;
+        this.chain = chain;
         this.connectionDelayMillis = connectionDelayMillis;
         this.fastCatchupTimeSecs = params.genesisBlock.getTimeSeconds();
         this.wallets = new ArrayList<Wallet>(1);
@@ -188,7 +190,7 @@ public class PeerGroup {
     // of the higher level {@code Peer}.  Received packets will first be decoded, then passed
     // {@code Peer}.  Sent packets will be created by the {@code Peer}, then encoded and sent.
     private ChannelPipelineFactory makePipelineFactory(
-            final NetworkParameters params, final BlockChain chain) {
+            final NetworkParameters params, final AbstractBlockChain chain) {
         return new ChannelPipelineFactory() {
             public ChannelPipeline getPipeline() throws Exception {
                 VersionMessage ver = getVersionMessage().duplicate();
@@ -726,6 +728,7 @@ public class PeerGroup {
      * {@link Peer#setFastCatchupTime(long)} for further explanation. Call this before starting block chain download.
      */
     public synchronized void setFastCatchupTimeSecs(long secondsSinceEpoch) {
+        Preconditions.checkState(!chain.shouldVerifyTransactions(), "Fast catchup is incompatible with fully verifying");
         fastCatchupTimeSecs = secondsSinceEpoch;
         if (downloadPeer != null) {
             downloadPeer.setFastCatchupTime(secondsSinceEpoch);