diff --git a/protocol/src/main/kotlin/org/openrs2/protocol/js5/Js5ResponseDecoder.kt b/protocol/src/main/kotlin/org/openrs2/protocol/js5/Js5ResponseDecoder.kt
index 888eb07c..19b06c40 100644
--- a/protocol/src/main/kotlin/org/openrs2/protocol/js5/Js5ResponseDecoder.kt
+++ b/protocol/src/main/kotlin/org/openrs2/protocol/js5/Js5ResponseDecoder.kt
@@ -62,7 +62,7 @@ public class Js5ResponseDecoder : ByteToMessageDecoder() {
 
         if (state == State.READ_DATA) {
             while (data.isWritable) {
-                val blockLen = min(511 - ((data.readableBytes() + 3) % 511), data.writableBytes())
+                val blockLen = min(511 - ((data.readableBytes() + 2) % 511), data.writableBytes())
                 val last = data.writableBytes() <= blockLen
 
                 val blockLenIncludingTrailer = if (last) {
diff --git a/protocol/src/main/kotlin/org/openrs2/protocol/js5/Js5ResponseEncoder.kt b/protocol/src/main/kotlin/org/openrs2/protocol/js5/Js5ResponseEncoder.kt
index d2650ef1..be7342e9 100644
--- a/protocol/src/main/kotlin/org/openrs2/protocol/js5/Js5ResponseEncoder.kt
+++ b/protocol/src/main/kotlin/org/openrs2/protocol/js5/Js5ResponseEncoder.kt
@@ -24,7 +24,7 @@ public object Js5ResponseEncoder : MessageToByteEncoder<Js5Response>(Js5Response
         }
         out.writeByte(compression)
 
-        out.writeBytes(msg.data, min(msg.data.readableBytes(), 507))
+        out.writeBytes(msg.data, min(msg.data.readableBytes(), 508))
 
         while (msg.data.isReadable) {
             out.writeByte(0xFF)
@@ -34,7 +34,7 @@ public object Js5ResponseEncoder : MessageToByteEncoder<Js5Response>(Js5Response
 
     override fun allocateBuffer(ctx: ChannelHandlerContext, msg: Js5Response, preferDirect: Boolean): ByteBuf {
         val dataLen = msg.data.readableBytes()
-        val len = 3 + dataLen + (3 + dataLen) / 511
+        val len = 3 + dataLen + (2 + dataLen) / 511
 
         return if (preferDirect) {
             ctx.alloc().ioBuffer(len, len)
diff --git a/protocol/src/test/kotlin/org/openrs2/protocol/js5/Js5ResponseDecoderTest.kt b/protocol/src/test/kotlin/org/openrs2/protocol/js5/Js5ResponseDecoderTest.kt
index 007d42f8..3301b2a5 100644
--- a/protocol/src/test/kotlin/org/openrs2/protocol/js5/Js5ResponseDecoderTest.kt
+++ b/protocol/src/test/kotlin/org/openrs2/protocol/js5/Js5ResponseDecoderTest.kt
@@ -14,23 +14,23 @@ import kotlin.test.assertEquals
 object Js5ResponseDecoderTest {
     @Test
     fun testDecode() {
-        testDecode("508.dat", "508-prefetch.dat", true)
-        testDecode("508.dat", "508-urgent.dat", false)
-
         testDecode("509.dat", "509-prefetch.dat", true)
         testDecode("509.dat", "509-urgent.dat", false)
 
-        testDecode("1019.dat", "1019-prefetch.dat", true)
-        testDecode("1019.dat", "1019-urgent.dat", false)
+        testDecode("510.dat", "510-prefetch.dat", true)
+        testDecode("510.dat", "510-urgent.dat", false)
 
         testDecode("1020.dat", "1020-prefetch.dat", true)
         testDecode("1020.dat", "1020-urgent.dat", false)
 
-        testDecode("1530.dat", "1530-prefetch.dat", true)
-        testDecode("1530.dat", "1530-urgent.dat", false)
+        testDecode("1021.dat", "1021-prefetch.dat", true)
+        testDecode("1021.dat", "1021-urgent.dat", false)
 
         testDecode("1531.dat", "1531-prefetch.dat", true)
         testDecode("1531.dat", "1531-urgent.dat", false)
+
+        testDecode("1532.dat", "1532-prefetch.dat", true)
+        testDecode("1532.dat", "1532-urgent.dat", false)
     }
 
     @Test
diff --git a/protocol/src/test/kotlin/org/openrs2/protocol/js5/Js5ResponseEncoderTest.kt b/protocol/src/test/kotlin/org/openrs2/protocol/js5/Js5ResponseEncoderTest.kt
index 45671736..f559c98c 100644
--- a/protocol/src/test/kotlin/org/openrs2/protocol/js5/Js5ResponseEncoderTest.kt
+++ b/protocol/src/test/kotlin/org/openrs2/protocol/js5/Js5ResponseEncoderTest.kt
@@ -12,23 +12,23 @@ import kotlin.test.assertEquals
 object Js5ResponseEncoderTest {
     @Test
     fun testEncode() {
-        testEncode("508.dat", "508-prefetch.dat", true)
-        testEncode("508.dat", "508-urgent.dat", false)
-
         testEncode("509.dat", "509-prefetch.dat", true)
         testEncode("509.dat", "509-urgent.dat", false)
 
-        testEncode("1019.dat", "1019-prefetch.dat", true)
-        testEncode("1019.dat", "1019-urgent.dat", false)
+        testEncode("510.dat", "510-prefetch.dat", true)
+        testEncode("510.dat", "510-urgent.dat", false)
 
         testEncode("1020.dat", "1020-prefetch.dat", true)
         testEncode("1020.dat", "1020-urgent.dat", false)
 
-        testEncode("1530.dat", "1530-prefetch.dat", true)
-        testEncode("1530.dat", "1530-urgent.dat", false)
+        testEncode("1021.dat", "1021-prefetch.dat", true)
+        testEncode("1021.dat", "1021-urgent.dat", false)
 
         testEncode("1531.dat", "1531-prefetch.dat", true)
         testEncode("1531.dat", "1531-urgent.dat", false)
+
+        testEncode("1532.dat", "1532-prefetch.dat", true)
+        testEncode("1532.dat", "1532-urgent.dat", false)
     }
 
     @Test
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/1020-prefetch.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/1020-prefetch.dat
index 7afdc6b3..1c134669 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/1020-prefetch.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/1020-prefetch.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/1020-urgent.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/1020-urgent.dat
index 57aa6a81..5126a2fd 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/1020-urgent.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/1020-urgent.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/1019-prefetch.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/1021-prefetch.dat
similarity index 81%
rename from protocol/src/test/resources/org/openrs2/protocol/js5/1019-prefetch.dat
rename to protocol/src/test/resources/org/openrs2/protocol/js5/1021-prefetch.dat
index 5d2ee5ce..b1730c54 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/1019-prefetch.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/1021-prefetch.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/1019-urgent.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/1021-urgent.dat
similarity index 81%
rename from protocol/src/test/resources/org/openrs2/protocol/js5/1019-urgent.dat
rename to protocol/src/test/resources/org/openrs2/protocol/js5/1021-urgent.dat
index 5efce678..102e9283 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/1019-urgent.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/1021-urgent.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/1019.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/1021.dat
similarity index 87%
rename from protocol/src/test/resources/org/openrs2/protocol/js5/1019.dat
rename to protocol/src/test/resources/org/openrs2/protocol/js5/1021.dat
index a8a624b6..5c9754df 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/1019.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/1021.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/1531-prefetch.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/1531-prefetch.dat
index fe8e66b4..0113c1a7 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/1531-prefetch.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/1531-prefetch.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/1531-urgent.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/1531-urgent.dat
index 09993f12..7778ed81 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/1531-urgent.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/1531-urgent.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/1530-urgent.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/1532-prefetch.dat
similarity index 83%
rename from protocol/src/test/resources/org/openrs2/protocol/js5/1530-urgent.dat
rename to protocol/src/test/resources/org/openrs2/protocol/js5/1532-prefetch.dat
index 22c4d38a..323db5b1 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/1530-urgent.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/1532-prefetch.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/1530-prefetch.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/1532-urgent.dat
similarity index 83%
rename from protocol/src/test/resources/org/openrs2/protocol/js5/1530-prefetch.dat
rename to protocol/src/test/resources/org/openrs2/protocol/js5/1532-urgent.dat
index eee39ab8..77ea56c5 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/1530-prefetch.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/1532-urgent.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/1530.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/1532.dat
similarity index 91%
rename from protocol/src/test/resources/org/openrs2/protocol/js5/1530.dat
rename to protocol/src/test/resources/org/openrs2/protocol/js5/1532.dat
index af31cb74..0b2b379c 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/1530.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/1532.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/509-prefetch.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/509-prefetch.dat
index 8b7b5f6e..bc2732b2 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/509-prefetch.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/509-prefetch.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/509-urgent.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/509-urgent.dat
index d97c7967..aa4e75b7 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/509-urgent.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/509-urgent.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/508-urgent.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/510-prefetch.dat
similarity index 74%
rename from protocol/src/test/resources/org/openrs2/protocol/js5/508-urgent.dat
rename to protocol/src/test/resources/org/openrs2/protocol/js5/510-prefetch.dat
index 040ac8bd..d98054b5 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/508-urgent.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/510-prefetch.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/508-prefetch.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/510-urgent.dat
similarity index 74%
rename from protocol/src/test/resources/org/openrs2/protocol/js5/508-prefetch.dat
rename to protocol/src/test/resources/org/openrs2/protocol/js5/510-urgent.dat
index baed755c..0e93725c 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/508-prefetch.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/510-urgent.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/508.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/510.dat
similarity index 75%
rename from protocol/src/test/resources/org/openrs2/protocol/js5/508.dat
rename to protocol/src/test/resources/org/openrs2/protocol/js5/510.dat
index 6500e76c..592509f2 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/508.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/510.dat differ
diff --git a/protocol/src/test/resources/org/openrs2/protocol/js5/invalid-block-trailer.dat b/protocol/src/test/resources/org/openrs2/protocol/js5/invalid-block-trailer.dat
index 2450d775..85b0c15d 100644
Binary files a/protocol/src/test/resources/org/openrs2/protocol/js5/invalid-block-trailer.dat and b/protocol/src/test/resources/org/openrs2/protocol/js5/invalid-block-trailer.dat differ