diff --git a/include/androidfw/AssetManager.h b/include/androidfw/AssetManager.h
index ac47900..a13dd16 100644
--- a/include/androidfw/AssetManager.h
+++ b/include/androidfw/AssetManager.h
@@ -231,7 +231,7 @@
      * corresponding overlay package.
      */
     bool createIdmap(const char* targetApkPath, const char* overlayApkPath,
-        uint32_t targetCrc, uint32_t overlayCrc, uint32_t** outData, uint32_t* outSize);
+        uint32_t targetCrc, uint32_t overlayCrc, uint32_t** outData, size_t* outSize);
 
 private:
     struct asset_path