diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index b276a2d48..436d960bc 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -1886,7 +1886,7 @@ void TypeChecker::expectType(Expression const& _expression, Type const& _expecte
 	{
 		auto literal = dynamic_cast<Literal const*>(&_expression);
 
-		if (literal && !boost::starts_with(literal->value(), "0x"))
+		if (literal && !literal->hasHexPrefix())
 			m_errorReporter.warning(
 				_expression.location(),
 				"Decimal literal assigned to bytesXX variable will be left-aligned. "
diff --git a/libsolidity/ast/AST.cpp b/libsolidity/ast/AST.cpp
index b929b6feb..54ded609e 100644
--- a/libsolidity/ast/AST.cpp
+++ b/libsolidity/ast/AST.cpp
@@ -530,20 +530,26 @@ IdentifierAnnotation& Identifier::annotation() const
 	return dynamic_cast<IdentifierAnnotation&>(*m_annotation);
 }
 
+bool Literal::hasHexPrefix() const
+{
+	if (token() != Token::Number)
+		return false;
+	return value().substr(0, 2) == "0x";
+}
+
 bool Literal::looksLikeAddress() const
 {
 	if (subDenomination() != SubDenomination::None)
 		return false;
-	if (token() != Token::Number)
+
+	if (!hasHexPrefix())
 		return false;
 
-	string lit = value();
-	return lit.substr(0, 2) == "0x" && abs(int(lit.length()) - 42) <= 1;
+	return abs(int(value().length()) - 42) <= 1;
 }
 
 bool Literal::passesAddressChecksum() const
 {
-	string lit = value();
-	solAssert(lit.substr(0, 2) == "0x", "Expected hex prefix");
-	return dev::passesAddressChecksum(lit, true);
+	solAssert(hasHexPrefix(), "Expected hex prefix");
+	return dev::passesAddressChecksum(value(), true);
 }
diff --git a/libsolidity/ast/AST.h b/libsolidity/ast/AST.h
index 835726921..24b16176c 100644
--- a/libsolidity/ast/AST.h
+++ b/libsolidity/ast/AST.h
@@ -1590,6 +1590,9 @@ public:
 
 	SubDenomination subDenomination() const { return m_subDenomination; }
 
+	/// @returns true if this is a number with a hex prefix.
+	bool hasHexPrefix() const;
+
 	/// @returns true if this looks like a checksummed address.
 	bool looksLikeAddress() const;
 	/// @returns true if it passes the address checksum test.