diff --git a/src/projector/otto.ts b/src/projector/otto.ts
index db3da1d..491ca40 100644
--- a/src/projector/otto.ts
+++ b/src/projector/otto.ts
@@ -63,7 +63,7 @@ export interface IFilePatch {
 	 * @param data The data to modify.
 	 * @returns Modified data.
 	 */
-	modify: (data: Uint8Array) => Uint8Array;
+	modify: (data: Uint8Array) => Promise<Uint8Array> | Uint8Array;
 
 	/**
 	 * Run after all patches.
diff --git a/src/projector/otto/windows.ts b/src/projector/otto/windows.ts
index fdd5ddd..d62d562 100644
--- a/src/projector/otto/windows.ts
+++ b/src/projector/otto/windows.ts
@@ -140,7 +140,8 @@ export class ProjectorOttoWindows extends ProjectorOtto {
 					if (!data) {
 						throw new Error(`Failed to read: ${entry.volumePath}`);
 					}
-					data = patch.modify(data);
+					// eslint-disable-next-line no-await-in-loop
+					data = await patch.modify(data);
 				}
 			}