--- configure.ac
+++ configure.ac
@@ -387,6 +387,7 @@ dnl ------------------------------------
 dnl
 dnl Internal macro to recursively expand all the options in the option list.
 dnl
+m4_define([m4_fst], [$1])
 define([XE_EXPAND_COMPLEX_OPTIONS],
 [m4_if([$2], [], [],
        [XE_EXPAND_COMPLEX_OPTION([$1], m4_fst($2))[]dnl