diff --git a/_constraints b/_constraints
index bd98885..9f49fd7 100644
--- a/_constraints
+++ b/_constraints
@@ -8,7 +8,7 @@
       <cpu>
         <flag>pclmulqdq</flag>
         <flag>sse2</flag>
-        <flag>sse4.1</flag>
+        <flag>sse4_1</flag>
       </cpu>
     </hardware>
   </overwrite>