diff --git a/fedireads/signatures.py b/fedireads/signatures.py
index 49d1a2d3..db46aa4b 100644
--- a/fedireads/signatures.py
+++ b/fedireads/signatures.py
@@ -39,7 +39,7 @@ def make_signature(sender, destination, date, digest):
     return ','.join('%s="%s"' % (k, v) for (k, v) in signature.items())
 
 def make_digest(data):
-    return 'SHA-256=' + b64encode(hashlib.sha512(data).digest()).decode('utf-8')
+    return 'SHA-256=' + b64encode(hashlib.sha256(data).digest()).decode('utf-8')
 
 def verify_digest(request):
     algorithm, digest = request.headers['digest'].split('=', 1)