diff --git a/matlab/dr1.m b/matlab/dr1.m
index fa65a555d..ff2fa9a24 100644
--- a/matlab/dr1.m
+++ b/matlab/dr1.m
@@ -462,6 +462,7 @@ if nrhx*nrhu1*nchx*nchu1 > 1e7
 	k1 = k1 + 1; 
       end
   end
+  B1 = B*B1;
 else
   B1 = B*dr.ghxx*kron(hx,hu1);
 end