diff --git a/refstack/api/validators.py b/refstack/api/validators.py
index 3150fa84..016085c0 100644
--- a/refstack/api/validators.py
+++ b/refstack/api/validators.py
@@ -128,7 +128,7 @@ class TestResultValidator(BaseValidator):
             try:
                 pubkey = request.headers.get('X-Public-Key', '')
                 try:
-                    pubkey.encode('utf-8')
+                    pubkey = pubkey.encode('utf-8')
                 except AttributeError:
                     # it's already in bytes
                     pass