diff --git a/src/main/resources/packs/create_wizardry/data/cmmodular/miapi/materials/metal/arcane_metal.json b/src/main/resources/packs/create_wizardry/data/cmmodular/miapi/materials/metal/arcane_metal_from_create_wizardry.json
similarity index 100%
rename from src/main/resources/packs/create_wizardry/data/cmmodular/miapi/materials/metal/arcane_metal.json
rename to src/main/resources/packs/create_wizardry/data/cmmodular/miapi/materials/metal/arcane_metal_from_create_wizardry.json
diff --git a/src/main/resources/packs/create_wizardry/data/cmmodular/miapi/materials/metal/mithril.json b/src/main/resources/packs/create_wizardry/data/cmmodular/miapi/materials/metal/mithril_from_create_wizardry.json
similarity index 100%
rename from src/main/resources/packs/create_wizardry/data/cmmodular/miapi/materials/metal/mithril.json
rename to src/main/resources/packs/create_wizardry/data/cmmodular/miapi/materials/metal/mithril_from_create_wizardry.json
diff --git a/tools/materials.py b/tools/materials.py
index 8f284f3..27e10a6 100644
--- a/tools/materials.py
+++ b/tools/materials.py
@@ -1426,7 +1426,13 @@ def _extend_with_extra_forms(pack="create_wizardry"):
         path = f"{base['group']}/{name}"
         EXTENSIONS.append({
             "pack": pack,
-            "path": path,
+            # The extension is filed under its own name, not the material's. A
+            # datapack file is identified by its path, so writing it to the
+            # material's path in a second pack does not add an extension - it
+            # replaces the material with one, whichever pack loads last. The
+            # extension then names itself as its own parent, MIAPI reads that as
+            # a cycle, and the material is gone for anyone with both mods.
+            "path": f"{path}_from_{pack}",
             "data": {
                 "parent": f"cmmodular:{path}",
                 "data": {