diff --git a/format.cc b/format.cc
index e71207ba..ff39d1fa 100644
--- a/format.cc
+++ b/format.cc
@@ -169,15 +169,19 @@ const Char *find_closing_brace(const Char *s, int num_open_braces = 1) {
   throw fmt::FormatError("unmatched '{' in format");
 }
 
-// Handles width specifier.
+// Checks if an argument is a valid printf width specifier and sets
+// left alignment if it is negative.
 struct WidthHandler : public fmt::internal::ArgVisitor<WidthHandler, ULongLong> {
  private:
   fmt::FormatSpec &spec_;
+
  public:
   explicit WidthHandler(fmt::FormatSpec &spec) : spec_(spec) {}
+
   ULongLong visit_unhandled_arg() {
     throw fmt::FormatError("width is not integer");
   }
+
   ULongLong visit_any_int(fmt::LongLong value) {
     ULongLong width = value;
     if (value < 0) {
@@ -186,6 +190,7 @@ struct WidthHandler : public fmt::internal::ArgVisitor<WidthHandler, ULongLong>
     }
     return width;
   }
+
   ULongLong visit_any_uint(ULongLong value) { return value; }
 };
 }  // namespace
@@ -565,7 +570,9 @@ void fmt::BasicWriter<Char>::FormatDouble(T value, const FormatSpec &spec) {
 template <typename Char>
 template <typename StringChar>
 void fmt::BasicWriter<Char>::write_str(
-    const internal::StringValue<StringChar> &str, const FormatSpec &spec) {
+    const internal::Arg::StringValue<StringChar> &str, const FormatSpec &spec) {
+  // Check if StringChar is convertible to Char.
+  internal::CharTraits<Char>::convert(StringChar());
   if (spec.type_ && spec.type_ != 's')
     internal::ReportUnknownType(spec.type_, "string");
   const StringChar *s = str.value;
@@ -840,7 +847,7 @@ void fmt::internal::PrintfParser<Char>::Format(
       writer.write_str(arg.string, spec);
       break;
     case Arg::WSTRING:
-      writer.write_str(internal::CharTraits<Char>::convert(arg.wstring), spec);
+      writer.write_str(arg.wstring, spec);
       break;
     case Arg::POINTER:
       if (spec.type_ && spec.type_ != 'p')
@@ -1048,7 +1055,7 @@ const Char *fmt::BasicFormatter<Char>::format(
       writer_.write_str(arg.string, spec);
       break;
     case Arg::WSTRING:
-      writer_.write_str(internal::CharTraits<Char>::convert(arg.wstring), spec);
+      writer_.write_str(arg.wstring, spec);
       break;
     case Arg::POINTER:
       if (spec.type_ && spec.type_ != 'p')
diff --git a/format.h b/format.h
index 1c5220ed..2b1ce9e1 100644
--- a/format.h
+++ b/format.h
@@ -340,12 +340,6 @@ void Array<T, SIZE>::append(const T *begin, const T *end) {
   size_ += num_elements;
 }
 
-template <typename Char>
-struct StringValue {
-  const Char *value;
-  std::size_t size;
-};
-
 template <typename Char>
 class BasicCharTraits {
  public:
@@ -373,11 +367,6 @@ public:
 
   static char convert(char value) { return value; }
 
-  static StringValue<char> convert(StringValue<wchar_t>) {
-    StringValue<char> s = {"", 0};
-    return s;
-  }
-
   template <typename T>
   static int FormatFloat(char *buffer, std::size_t size,
       const char *format, unsigned width, int precision, T value);
@@ -391,8 +380,6 @@ class CharTraits<wchar_t> : public BasicCharTraits<wchar_t> {
   static wchar_t convert(char value) { return value; }
   static wchar_t convert(wchar_t value) { return value; }
 
-  static StringValue<wchar_t> convert(StringValue<wchar_t> s) { return s; }
-
   static const wchar_t *check(const wchar_t *s) { return s; }
 
   template <typename T>
@@ -600,6 +587,12 @@ struct Arg {
   };
   Type type;
 
+  template <typename Char>
+  struct StringValue {
+    const Char *value;
+    std::size_t size;
+  };
+
   typedef void (*FormatFunc)(
       void *formatter, const void *arg, const void *format_str);
 
@@ -773,10 +766,10 @@ class ArgVisitor {
   Result visit_char(int) {
     return FMT_DISPATCH(visit_unhandled_arg());
   }
-  Result visit_string(StringValue<char>) {
+  Result visit_string(Arg::StringValue<char>) {
     return FMT_DISPATCH(visit_unhandled_arg());
   }
-  Result visit_wstring(StringValue<wchar_t>) {
+  Result visit_wstring(Arg::StringValue<wchar_t>) {
     return FMT_DISPATCH(visit_unhandled_arg());
   }
   Result visit_pointer(const void *) {
@@ -1347,7 +1340,7 @@ class BasicWriter {
 
   template <typename StringChar>
   void write_str(
-      const internal::StringValue<StringChar> &str, const FormatSpec &spec);
+      const internal::Arg::StringValue<StringChar> &str, const FormatSpec &spec);
 
   // This method is private to disallow writing a wide string to a
   // char stream and vice versa. If you want to print a wide string
diff --git a/test/util-test.cc b/test/util-test.cc
index f93258db..0b7facc0 100644
--- a/test/util-test.cc
+++ b/test/util-test.cc
@@ -254,10 +254,10 @@ struct TestVisitor : fmt::internal::ArgVisitor<TestVisitor, Result> {
   Result visit_double(double value) { return value; }
   Result visit_long_double(long double value) { return value; }
   Result visit_char(int value) { return static_cast<char>(value); }
-  Result visit_string(fmt::internal::StringValue<char> s) { return s.value; }
-  Result visit_wstring(fmt::internal::StringValue<wchar_t> s) { return s.value; }
+  Result visit_string(Arg::StringValue<char> s) { return s.value; }
+  Result visit_wstring(Arg::StringValue<wchar_t> s) { return s.value; }
   Result visit_pointer(const void *p) { return p; }
-  Result visit_custom(fmt::internal::Arg::CustomValue c) {
+  Result visit_custom(Arg::CustomValue c) {
     return *static_cast<const ::Test*>(c.value);
   }
 };