diff --git a/tests/AcDream.Core.Net.Tests/Messages/UpdateMotionTests.cs b/tests/AcDream.Core.Net.Tests/Messages/UpdateMotionTests.cs
index ff53d48..83b0ab4 100644
--- a/tests/AcDream.Core.Net.Tests/Messages/UpdateMotionTests.cs
+++ b/tests/AcDream.Core.Net.Tests/Messages/UpdateMotionTests.cs
@@ -36,19 +36,19 @@ public class UpdateMotionTests
         //   u32 opcode = 0xF74C
         //   u32 guid
         //   u16 instanceSeq
-        //   u16 movementSeq + u16 serverControlSeq + u8 isAutonomous + 3 pad (= 8 bytes total header)
+        //   u16 movementSeq + u16 serverControlSeq + u8 isAutonomous + 1 pad (= 6 bytes total header, per ACE Align())
         //   u8 movementType = 0 (Invalid)
         //   u8 motionFlags = 0
         //   u16 currentStyle (outer MovementData field) = 0x0042
         //   u32 packed = CurrentStyle flag (0x1) only
         //   u16 inner currentStyle = 0x0005 (overrides outer per InterpretedMotionState semantics)
-        var body = new byte[4 + 4 + 2 + 8 + 4 + 4 + 2];
+        var body = new byte[4 + 4 + 2 + 6 + 4 + 4 + 2];
         int p = 0;
         BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(p), 0xF74Cu); p += 4;
         BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(p), 0x12345678u); p += 4;
         BinaryPrimitives.WriteUInt16LittleEndian(body.AsSpan(p), 0x0001); p += 2;
         // 8-byte header slot — leave zero
-        p += 8;
+        p += 6;
         body[p++] = 0;     // movementType = Invalid
         body[p++] = 0;     // motionFlags
         BinaryPrimitives.WriteUInt16LittleEndian(body.AsSpan(p), 0x0042); p += 2;
@@ -66,12 +66,12 @@ public class UpdateMotionTests
     public void ParsesStanceAndForwardCommand()
     {
         // Flags = CurrentStyle (0x1) | ForwardCommand (0x2)
-        var body = new byte[4 + 4 + 2 + 8 + 4 + 4 + 2 + 2];
+        var body = new byte[4 + 4 + 2 + 6 + 4 + 4 + 2 + 2];
         int p = 0;
         BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(p), 0xF74Cu); p += 4;
         BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(p), 0xABCDEF01u); p += 4;
         BinaryPrimitives.WriteUInt16LittleEndian(body.AsSpan(p), 0x0010); p += 2;
-        p += 8;   // MovementData header slot
+        p += 6;   // MovementData header slot
         body[p++] = 0;
         body[p++] = 0;
         BinaryPrimitives.WriteUInt16LittleEndian(body.AsSpan(p), 0x0000); p += 2;  // outer style = 0
@@ -93,12 +93,12 @@ public class UpdateMotionTests
         // currentStyle nor the forward command are present in the payload,
         // so the parser should fall back to the MovementData outer stance
         // field and leave ForwardCommand null.
-        var body = new byte[4 + 4 + 2 + 8 + 4 + 4];
+        var body = new byte[4 + 4 + 2 + 6 + 4 + 4];
         int p = 0;
         BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(p), 0xF74Cu); p += 4;
         BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(p), 0x55555555u); p += 4;
         BinaryPrimitives.WriteUInt16LittleEndian(body.AsSpan(p), 0); p += 2;
-        p += 8;
+        p += 6;
         body[p++] = 0;
         body[p++] = 0;
         BinaryPrimitives.WriteUInt16LittleEndian(body.AsSpan(p), 0x00AA); p += 2;
@@ -116,12 +116,12 @@ public class UpdateMotionTests
         // movementType != 0 means one of the Move* variants we don't parse.
         // The parser must still return a valid Parsed with the outer stance
         // and a null ForwardCommand rather than failing the whole message.
-        var body = new byte[4 + 4 + 2 + 8 + 4];
+        var body = new byte[4 + 4 + 2 + 6 + 4];
         int p = 0;
         BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(p), 0xF74Cu); p += 4;
         BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(p), 0x99999999u); p += 4;
         BinaryPrimitives.WriteUInt16LittleEndian(body.AsSpan(p), 0); p += 2;
-        p += 8;
+        p += 6;
         body[p++] = 1;    // movementType = MoveToObject (non-Invalid)
         body[p++] = 0;
         BinaryPrimitives.WriteUInt16LittleEndian(body.AsSpan(p), 0x00CC); p += 2;