diff --git a/src/Jamrules b/src/Jamrules
index 063761db9..fad0b9aa1 100644
--- a/src/Jamrules
+++ b/src/Jamrules
@@ -145,9 +145,8 @@ rule TargetDirectory
             OPTIM = -O0 ;
         }
         else {
-            SubDirCcFlags -DNDEBUG -mtune=$(CPU) ;
-            SubDirC++Flags -DNDEBUG -mtune=$(CPU) ;
-            OPTIM = -O3 -fno-strict-aliasing ;
+            SubDirCcFlags -DNDEBUG -march=$(CPU) -mtune=$(CPU) ;
+            SubDirC++Flags -DNDEBUG -march=$(CPU) -mtune=$(CPU) ;
         }
 }