diff --git a/Integrations/azure/akv-sign/gramine-sgx-akv-sign b/Integrations/azure/akv-sign/gramine-sgx-akv-sign
index e96fbe7..3a1df09 100755
--- a/Integrations/azure/akv-sign/gramine-sgx-akv-sign
+++ b/Integrations/azure/akv-sign/gramine-sgx-akv-sign
@@ -79,7 +79,7 @@ def main(output, libpal, key, url, manifest_file, sigfile, verbose):
 
     expanded = manifest.expand_all_trusted_files()
 
-    with open(output, 'w', encoding='utf-8') as f:
+    with open(output, 'wb') as f:
         manifest.dump(f)
 
     if not sigfile: