diff --git a/libsolidity/ast/Types.cpp b/libsolidity/ast/Types.cpp
index 9dd3cd5e9..ebe935502 100644
--- a/libsolidity/ast/Types.cpp
+++ b/libsolidity/ast/Types.cpp
@@ -1408,7 +1408,7 @@ BoolResult StringLiteralType::isImplicitlyConvertibleTo(Type const& _convertTo)
 		return
 			arrayType->isByteArray() &&
 			!(arrayType->dataStoredIn(DataLocation::Storage) && arrayType->isPointer()) &&
-			!(arrayType->isString() && !isValidUTF8());
+			!(arrayType->isString() && !util::validateUTF8(value()));
 	else
 		return false;
 }
@@ -1442,11 +1442,6 @@ TypePointer StringLiteralType::mobileType() const
 	return TypeProvider::stringMemory();
 }
 
-bool StringLiteralType::isValidUTF8() const
-{
-	return util::validateUTF8(m_value);
-}
-
 FixedBytesType::FixedBytesType(unsigned _bytes): m_bytes(_bytes)
 {
 	solAssert(
diff --git a/libsolidity/ast/Types.h b/libsolidity/ast/Types.h
index 938b3f886..9b32475ca 100644
--- a/libsolidity/ast/Types.h
+++ b/libsolidity/ast/Types.h
@@ -629,8 +629,6 @@ public:
 	std::string toString(bool) const override;
 	TypePointer mobileType() const override;
 
-	bool isValidUTF8() const;
-
 	std::string const& value() const { return m_value; }
 
 protected: