diff --git a/core/src/main/java/com/google/bitcoin/core/BitcoinSerializer.java b/core/src/main/java/com/google/bitcoin/core/BitcoinSerializer.java
index ee3df9d99..c397a9e8b 100644
--- a/core/src/main/java/com/google/bitcoin/core/BitcoinSerializer.java
+++ b/core/src/main/java/com/google/bitcoin/core/BitcoinSerializer.java
@@ -103,7 +103,7 @@ public class BitcoinSerializer {
         }
 
         byte[] header = new byte[4 + COMMAND_LEN + 4 + 4 /* checksum */];
-        uint32ToByteArrayBE(params.packetMagic, header, 0);
+        uint32ToByteArrayBE(params.getPacketMagic(), header, 0);
 
         // The header array is initialized to zero by Java so we don't have to worry about
         // NULL terminating the string here.
@@ -272,7 +272,7 @@ public class BitcoinSerializer {
             }
             // We're looking for a run of bytes that is the same as the packet magic but we want to ignore partial
             // magics that aren't complete. So we keep track of where we're up to with magicCursor.
-            int expectedByte = 0xFF & (int) (params.packetMagic >>> (magicCursor * 8));
+            int expectedByte = 0xFF & (int) (params.getPacketMagic() >>> (magicCursor * 8));
             if (b == expectedByte) {
                 magicCursor--;
                 if (magicCursor < 0) {
diff --git a/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java b/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java
index 02f2e9362..e1020db10 100644
--- a/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java
+++ b/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java
@@ -62,8 +62,7 @@ public class NetworkParameters implements Serializable {
     /** What the easiest allowable proof of work should be. */
     public /*final*/ BigInteger proofOfWorkLimit;
     private final int port;
-    /** The header bytes that identify the start of a packet on this network. */
-    public final long packetMagic;
+    private final long packetMagic;
     /**
      * First byte of a base58 encoded address. See {@link Address}. This is the same as acceptableAddressCodes[0] and
      * is the one used for "normal" addresses. Other types of address may be encountered with version codes found in
@@ -397,4 +396,9 @@ public class NetworkParameters implements Serializable {
     public int getPort() {
         return port;
     }
+
+    /** The header bytes that identify the start of a packet on this network. */
+    public long getPacketMagic() {
+        return packetMagic;
+    }
 }
diff --git a/core/src/main/java/com/google/bitcoin/utils/BlockFileLoader.java b/core/src/main/java/com/google/bitcoin/utils/BlockFileLoader.java
index 07f58062c..95b7e2410 100644
--- a/core/src/main/java/com/google/bitcoin/utils/BlockFileLoader.java
+++ b/core/src/main/java/com/google/bitcoin/utils/BlockFileLoader.java
@@ -124,18 +124,18 @@ public class BlockFileLoader implements Iterable<Block>, Iterator<Block> {
             try {
                 int nextChar = currentFileStream.read();
                 while (nextChar != -1) {
-                    if (nextChar != ((params.packetMagic >>> 24) & 0xff)) {
+                    if (nextChar != ((params.getPacketMagic() >>> 24) & 0xff)) {
                         nextChar = currentFileStream.read();
                         continue;
                     }
                     nextChar = currentFileStream.read();
-                    if (nextChar != ((params.packetMagic >>> 16) & 0xff))
+                    if (nextChar != ((params.getPacketMagic() >>> 16) & 0xff))
                         continue;
                     nextChar = currentFileStream.read();
-                    if (nextChar != ((params.packetMagic >>> 8) & 0xff))
+                    if (nextChar != ((params.getPacketMagic() >>> 8) & 0xff))
                         continue;
                     nextChar = currentFileStream.read();
-                    if (nextChar == (params.packetMagic & 0xff))
+                    if (nextChar == (params.getPacketMagic() & 0xff))
                         break;
                 }
                 byte[] bytes = new byte[4];
diff --git a/core/src/test/java/com/google/bitcoin/core/FullBlockTestGenerator.java b/core/src/test/java/com/google/bitcoin/core/FullBlockTestGenerator.java
index dea737769..8e7f2a14e 100644
--- a/core/src/test/java/com/google/bitcoin/core/FullBlockTestGenerator.java
+++ b/core/src/test/java/com/google/bitcoin/core/FullBlockTestGenerator.java
@@ -85,10 +85,10 @@ public class FullBlockTestGenerator {
             public boolean add(BlockAndValidity element) {
                 if (outStream != null) {
                     try {
-                        outStream.write((int) (params.packetMagic >>> 24));
-                        outStream.write((int) (params.packetMagic >>> 16));
-                        outStream.write((int) (params.packetMagic >>> 8));
-                        outStream.write((int) (params.packetMagic >>> 0));
+                        outStream.write((int) (params.getPacketMagic() >>> 24));
+                        outStream.write((int) (params.getPacketMagic() >>> 16));
+                        outStream.write((int) (params.getPacketMagic() >>> 8));
+                        outStream.write((int) (params.getPacketMagic() >>> 0));
                         byte[] block = element.block.bitcoinSerialize();
                         byte[] length = new byte[4];
                         Utils.uint32ToByteArrayBE(block.length, length, 0);