diff --git a/lemur/certificates/schemas.py b/lemur/certificates/schemas.py
index bc7ff1b0..42e444bc 100644
--- a/lemur/certificates/schemas.py
+++ b/lemur/certificates/schemas.py
@@ -147,8 +147,7 @@ class CertificateInputSchema(CertificateCreationSchema):
             elif not data["extensions"]["subAltNames"].get("names"):
                 data["extensions"]["subAltNames"]["names"] = []
 
-            if not data["extensions"]["subAltNames"]["names"]:
-                data["extensions"]["subAltNames"]["names"] += csr_sans
+            data["extensions"]["subAltNames"]["names"] = csr_sans
         return missing.convert_validity_years(data)