diff --git a/lemur/certificates/schemas.py b/lemur/certificates/schemas.py
index 1352f796..b807c760 100644
--- a/lemur/certificates/schemas.py
+++ b/lemur/certificates/schemas.py
@@ -123,7 +123,7 @@ class CertificateInputSchema(CertificateCreationSchema):
                 data['extensions']['subAltNames'] = {
                     'names': []
                 }
-            elif not data['extensions']['subAltNames']['names']:
+            elif not data['extensions']['subAltNames'].get('names'):
                 data['extensions']['subAltNames']['names'] = []
             data['extensions']['subAltNames']['names'] += csr_sans
         return missing.convert_validity_years(data)