diff --git a/m4/ipopt.m4 b/m4/ipopt.m4
index 04639acaf1b8415dd024b4f51d9add70f426ae02..44b5007f70e211e94527ee33c582a121b122e4c3 100644
--- a/m4/ipopt.m4
+++ b/m4/ipopt.m4
@@ -1,6 +1,6 @@
 # searches for ipopt headers and libs
 
-AC_DEFUN([DUNE_IPOPT], [
+AC_DEFUN([DUNE_IPOPT],[
   AC_REQUIRE([AC_PROG_CXX])
 
   AC_ARG_WITH(ipopt,