diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index 72dcb89af..8346b56e0 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -204,7 +204,7 @@ RTLIL::Const::Const()
 	flags = RTLIL::CONST_FLAG_NONE;
 }
 
-RTLIL::Const::Const(std::string str)
+RTLIL::Const::Const(const std::string &str)
 {
 	flags = RTLIL::CONST_FLAG_STRING;
 	bits.reserve(str.size() * 8);
@@ -243,14 +243,6 @@ RTLIL::Const::Const(const std::vector<bool> &bits)
 		this->bits.emplace_back(b ? State::S1 : State::S0);
 }
 
-RTLIL::Const::Const(const RTLIL::Const &c)
-{
-	flags = c.flags;
-	this->bits.reserve(c.size());
-	for (const auto &b : c.bits)
-		this->bits.push_back(b);
-}
-
 bool RTLIL::Const::operator <(const RTLIL::Const &other) const
 {
 	if (bits.size() != other.bits.size())
diff --git a/kernel/rtlil.h b/kernel/rtlil.h
index d8300f159..7a0b6b9c7 100644
--- a/kernel/rtlil.h
+++ b/kernel/rtlil.h
@@ -636,12 +636,12 @@ struct RTLIL::Const
 	std::vector<RTLIL::State> bits;
 
 	Const();
-	Const(std::string str);
+	Const(const std::string &str);
 	Const(int val, int width = 32);
 	Const(RTLIL::State bit, int width = 1);
 	Const(const std::vector<RTLIL::State> &bits) : bits(bits) { flags = CONST_FLAG_NONE; }
 	Const(const std::vector<bool> &bits);
-	Const(const RTLIL::Const &c);
+	Const(const RTLIL::Const &c) = default;
 	RTLIL::Const &operator =(const RTLIL::Const &other) = default;
 
 	bool operator <(const RTLIL::Const &other) const;