diff --git a/core/pom.xml b/core/pom.xml
index 261add1a4..16c4a19db 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -4,7 +4,7 @@
   <parent>
     <groupId>com.threerings</groupId>
     <artifactId>narya-parent</artifactId>
-    <version>1.21</version>
+    <version>1.22</version>
   </parent>
 
   <artifactId>narya</artifactId>
diff --git a/core/src/main/java/com/threerings/presents/data/InvocationMarshaller.java b/core/src/main/java/com/threerings/presents/data/InvocationMarshaller.java
index f6147343f..720088b1d 100644
--- a/core/src/main/java/com/threerings/presents/data/InvocationMarshaller.java
+++ b/core/src/main/java/com/threerings/presents/data/InvocationMarshaller.java
@@ -7,7 +7,9 @@ package com.threerings.presents.data;
 
 import java.io.IOException;
 
+import com.threerings.io.GenStreamUtil;
 import com.threerings.io.ObjectInputStream;
+import com.threerings.io.ObjectOutputStream;
 import com.threerings.io.Streamable;
 
 import com.threerings.presents.client.Client;
@@ -244,17 +246,37 @@ public class InvocationMarshaller<T extends ClientObject>
     }
 
     /**
-     * A custom reader method for {@link Streamable}.
+     * A custom reader method for {@link Streamable}. Reads {@code _invOid}/{@code _invCode}
+     * explicitly (by name, in declaration order) rather than via {@code defaultReadObject()} so the
+     * field order is deterministic across ART and HotSpot (Epic A1 Phase 5, approach b) — byte
+     * identical to the old reflective read. Marshaller SUBCLASSES intentionally have NO generated
+     * read/writeObject (they are field-free) so they inherit this method, which also performs the
+     * side-effect the generated flatten-mode streamers would otherwise skip: binding {@link #_invdir}
+     * from the stream's client. That binding is the whole reason this is a hand-written custom
+     * reader; a subclass overriding it would leave {@code _invdir} null and NPE on the first request.
      */
     public void readObject (ObjectInputStream in)
         throws IOException, ClassNotFoundException
     {
-        in.defaultReadObject();
+        GenStreamUtil.readField(InvocationMarshaller.class, "_invOid", this, in);
+        GenStreamUtil.readField(InvocationMarshaller.class, "_invCode", this, in);
         if (in instanceof ClientObjectInputStream) {
             _invdir = ((ClientObjectInputStream)in).client.getInvocationDirector();
         }
     }
 
+    /**
+     * A custom writer method for {@link Streamable}; mirrors {@link #readObject} (explicit,
+     * deterministic field order) so field-free marshaller subclasses inherit it. Byte identical to
+     * the previous reflective default write.
+     */
+    public void writeObject (ObjectOutputStream out)
+        throws IOException
+    {
+        GenStreamUtil.writeField(InvocationMarshaller.class, "_invOid", this, out);
+        GenStreamUtil.writeField(InvocationMarshaller.class, "_invCode", this, out);
+    }
+
     @Override
     public String toString ()
     {
diff --git a/pom.xml b/pom.xml
index a027437b0..27edaf7cf 100644
--- a/pom.xml
+++ b/pom.xml
@@ -5,7 +5,7 @@
   <groupId>com.threerings</groupId>
   <artifactId>narya-parent</artifactId>
   <packaging>pom</packaging>
-  <version>1.21</version>
+  <version>1.22</version>
 
   <name>Narya Parent</name>
   <description>Facilities for making networked multiplayer games.</description>
diff --git a/tools/pom.xml b/tools/pom.xml
index b4f1e55ad..3eab7bfdd 100644
--- a/tools/pom.xml
+++ b/tools/pom.xml
@@ -4,7 +4,7 @@
   <parent>
     <groupId>com.threerings</groupId>
     <artifactId>narya-parent</artifactId>
-    <version>1.21</version>
+    <version>1.22</version>
   </parent>
 
   <artifactId>narya-tools</artifactId>