--- automake-1.11.2/automake.in
+++ automake-1.11.2/automake.in
@@ -4156,7 +4156,7 @@ sub substitute_ac_subst_variables_worker($)
 sub substitute_ac_subst_variables ($)
 {
   my ($text) = @_;
-  $text =~ s/\${([^ \t=:+{}]+)}/&substitute_ac_subst_variables_worker ($1)/ge;
+  $text =~ s/\$\{([^ \t=:+{}]+)}/&substitute_ac_subst_variables_worker ($1)/ge;
   return $text;
 }