diff --git a/mbEditorPro2.0/JSON_CHANGES.md b/mbEditorPro2.0/JSON_CHANGES.md
index 258fa70..65fad73 100644
--- a/mbEditorPro2.0/JSON_CHANGES.md
+++ b/mbEditorPro2.0/JSON_CHANGES.md
@@ -25,13 +25,11 @@ The binary `.cache` format did not change. Every resource in
 | Signed 32-bit fields | Values that were `4294967295` are now `-1`, `4294967286` is now `-10`, and so on | Accept negative integers |
 | Grant attribute and power keys | First element of each pair is now a name string when the hash is known | Accept a string or an integer; convert names with `string_to_hash` |
 
-Old JSON dumps are not fully compatible. `4294967295` and `-1` are the same
-four bytes, but the packer now writes signed fields with `struct.pack('<i')`,
-which rejects values above `2147483647` with `struct.error`. The sample dump has
-such values (`rank_hirelings`, `rank_rank`, `attr_value`). Re-run
-`unpack cobjects` to regenerate old dumps, or convert those values by
-subtracting `4294967296`, before packing. Integer grant keys in old dumps still
-pack unchanged.
+Old JSON dumps still pack. `4294967295` and `-1` are the same four bytes, and
+`ResStream.write_long` accepts either form: values from `2147483648` to
+`4294967295` are converted to their signed equivalent before packing. Integer
+grant keys in old dumps also pack unchanged. Re-running `unpack cobjects` is
+only needed to see the new signed values and grant key names in the JSON.
 
 ## 1. Signed 32-bit fields
 
diff --git a/mbEditorPro2.0/arcane/util/ResStream.py b/mbEditorPro2.0/arcane/util/ResStream.py
index 247de1d..cc5475e 100644
--- a/mbEditorPro2.0/arcane/util/ResStream.py
+++ b/mbEditorPro2.0/arcane/util/ResStream.py
@@ -77,6 +77,9 @@ class ResStream:
         self.buffer.write(data)
 
     def write_long(self, value):
+        # Older dumps stored signed fields as unsigned; both forms are the same bytes.
+        if 0x7FFFFFFF < value <= 0xFFFFFFFF:
+            value -= 0x100000000
         data = struct.pack('<i', value)
         self.buffer.write(data)