diff --git a/mingw-w64-headers/configure b/mingw-w64-headers/configure
index c0f00b0..43fe5e6 100755
--- a/mingw-w64-headers/configure
+++ b/mingw-w64-headers/configure
@@ -2475,7 +2475,7 @@ fi
 $as_echo "$with_widl" >&6; }
 
 if test "x$with_widl" = xno; then :
-
+  unset WIDL
 else
 
   if test "x$srcdir" = x.; then :
diff --git a/mingw-w64-headers/configure.ac b/mingw-w64-headers/configure.ac
index 4c20762..eda8d76 100644
--- a/mingw-w64-headers/configure.ac
+++ b/mingw-w64-headers/configure.ac
@@ -27,7 +27,7 @@ AC_ARG_WITH([widl],
   [AS_VAR_SET([with_widl],[no])])
 AC_MSG_RESULT([$with_widl])
 
-AS_VAR_IF([with_widl],[no],[],[
+AS_VAR_IF([with_widl],[no],[unset WIDL],[
   AS_VAR_IF([srcdir],[.],[],
     [AC_MSG_WARN([--with-widl used in out of the tree compilation.  Existing generated files will not be modified.])])
   AC_PATH_PROGS([WIDL], [$host-widl widl], [], [$with_widl])