diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index 8daf2c821..adcc5f41c 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -264,10 +264,10 @@ std::string& Const::get_str() {
 	return *get_if_str();
 }
 
-RTLIL::Const::Const(const std::string &str)
+RTLIL::Const::Const(std::string str)
 {
 	flags = RTLIL::CONST_FLAG_STRING;
-	new ((void*)&str_) std::string(str);
+	new ((void*)&str_) std::string(std::move(str));
 	tag = backing_tag::string;
 }
 
diff --git a/kernel/rtlil.h b/kernel/rtlil.h
index 5271a3111..74a57e554 100644
--- a/kernel/rtlil.h
+++ b/kernel/rtlil.h
@@ -859,7 +859,7 @@ private:
 
 public:
 	Const() : flags(RTLIL::CONST_FLAG_NONE), tag(backing_tag::bits), bits_(std::vector<RTLIL::State>()) {}
-	Const(const std::string &str);
+	Const(std::string str);
 	Const(long long val); // default width is 32
 	Const(long long val, int width);
 	Const(RTLIL::State bit, int width = 1);