diff --git a/compilers/Cyber_Compiler.rb b/compilers/Cyber_Compiler.rb
index 2e7cebc..1524c0a 100644
--- a/compilers/Cyber_Compiler.rb
+++ b/compilers/Cyber_Compiler.rb
@@ -123,7 +123,7 @@ def compile_domain(domain_name, problem_name, operators, methods, predicates, st
         define_methods << "\n\nstatic bool #{name}_#{dec[0]}_(const Task *task)\n{\n  const VALUE *parameters = task->parameters;#{param_str}"
         equality = []
         define_methods_comparison = ''
-        f = dec[1]
+        f = dec[1].dup
         precond_pos = dec[2].sort_by {|pre| (pre & param).size * -100 - (pre & f).size}
         precond_pos.reject! {|pre,*terms|
           if (terms & f).empty?
diff --git a/compilers/Hyper_Compiler.rb b/compilers/Hyper_Compiler.rb
index 9f6ea68..6da76c2 100644
--- a/compilers/Hyper_Compiler.rb
+++ b/compilers/Hyper_Compiler.rb
@@ -114,7 +114,7 @@ def compile_domain(domain_name, problem_name, operators, methods, predicates, st
         define_methods << "\n  def #{name}_#{dec[0]}#{variables}"
         equality = []
         define_methods_comparison = ''
-        f = dec[1]
+        f = dec[1].dup
         precond_pos = dec[2].sort_by {|pre| (pre & param).size * -100 - (pre & f).size}
         precond_pos.reject! {|pre,*terms|
           if (terms & f).empty?