diff --git a/ares/configure.ac b/ares/configure.ac
index 9d3d897e547aff65e4e28d6f5031cb0e1757db02..2d09dbacc0abb7eada8e31c35e75b6e378f92985 100644
--- a/ares/configure.ac
+++ b/ares/configure.ac
@@ -64,15 +64,11 @@ AC_HELP_STRING([--disable-debug],[Disable debug options]),
 )
 
 dnl skip libtool C++ and Fortran compiler checks
-m4_undefine([AC_PROG_CXX])
 m4_defun([AC_PROG_CXX],[])
-m4_undefine([AC_PROG_F77])
 m4_defun([AC_PROG_F77],[])
 
 dnl skip libtool C++ and Fortran linker checks
-m4_undefine([AC_LIBTOOL_CXX])
 m4_defun([AC_LIBTOOL_CXX],[])
-m4_undefine([AC_LIBTOOL_F77])
 m4_defun([AC_LIBTOOL_F77],[])
 
 dnl libtool setup
diff --git a/configure.ac b/configure.ac
index 5c13d7c9e6e288010309cb2e6b975732cb581a50..b8a16f8e97716210b0501b55eb7818cb2a6d7e72 100644
--- a/configure.ac
+++ b/configure.ac
@@ -116,15 +116,11 @@ dnl support building of Windows DLLs
 AC_LIBTOOL_WIN32_DLL
 
 dnl skip libtool C++ and Fortran compiler checks
-m4_undefine([AC_PROG_CXX])
 m4_defun([AC_PROG_CXX],[])
-m4_undefine([AC_PROG_F77])
 m4_defun([AC_PROG_F77],[])
 
 dnl skip libtool C++ and Fortran linker checks
-m4_undefine([AC_LIBTOOL_CXX])
 m4_defun([AC_LIBTOOL_CXX],[])
-m4_undefine([AC_LIBTOOL_F77])
 m4_defun([AC_LIBTOOL_F77],[])
 
 dnl libtool setup