diff --git a/configure.ac b/configure.ac
index 4fa308c..c7b731c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -67,7 +67,7 @@ fi
 dnl Include support for regex in upstream proxies?
 AH_TEMPLATE([UPSTREAM_REGEX],
             [Include support for connecting to an upstream proxy based on a regex.])
-TP_ARG_ENABLE(upstream_regex,
+TP_ARG_ENABLE(upstream-regex,
               [Enable upstream proxying (default is YES)],
               yes)
 if test x"$upstream_regex_enabled" = x"yes"; then
diff --git a/m4macros/argenable.m4 b/m4macros/argenable.m4
index e21604a..913b976 100644
--- a/m4macros/argenable.m4
+++ b/m4macros/argenable.m4
@@ -10,10 +10,11 @@ dnl This macro also defines on variable in the form "option_enabled"
 dnl set to either "yes" or "no".
 dnl
 AC_DEFUN([TP_ARG_ENABLE],
-[AC_ARG_ENABLE([$1],
+[var=`echo $1 | tr - _`
+AC_ARG_ENABLE([$1],
   AS_HELP_STRING([--enable-$1], [$2]),
   [case "${enableval}" in
-    yes)  $1_enabled=yes ;;
-    no)   $1_enabled=no ;;
+    yes)  eval ${var}_enabled=yes ;;
+    no)   eval ${var}_enabled=no ;;
     *)    AC_MSG_ERROR([bad value ${enableval} for --enable-$1]) ;;
-   esac],[$1_enabled=$3])])
+   esac],[eval ${var}_enabled=$3])])