diff --git a/taglib/toolkit/tstring.cpp b/taglib/toolkit/tstring.cpp
index c4a628a6..cca15e10 100644
--- a/taglib/toolkit/tstring.cpp
+++ b/taglib/toolkit/tstring.cpp
@@ -38,11 +38,10 @@ namespace
   using namespace TagLib;
 
   // Returns the native format of std::wstring.
-  String::Type wcharByteOrder()
+  constexpr String::Type wcharByteOrder()
   {
-    if(Utils::systemByteOrder() == Utils::LittleEndian)
-      return String::UTF16LE;
-    return String::UTF16BE;
+    return Utils::systemByteOrder() == Utils::LittleEndian ? String::UTF16LE
+                                                           : String::UTF16BE;
   }
 
   // Converts a Latin-1 string into UTF-16(without BOM/CPU byte order)
@@ -172,17 +171,15 @@ String::String(const std::string &s, Type t) :
   }
 }
 
+String::String(const wstring &s) :
+ String(s, wcharByteOrder())
+{
+}
+
 String::String(const wstring &s, Type t) :
   d(std::make_shared<StringPrivate>())
 {
   if(t == UTF16 || t == UTF16BE || t == UTF16LE) {
-    // This looks ugly but needed for the compatibility with TagLib1.8.
-    // Should be removed in TabLib2.0.
-    if (t == UTF16BE)
-      t = wcharByteOrder();
-    else if (t == UTF16LE)
-      t = (wcharByteOrder() == UTF16LE ? UTF16BE : UTF16LE);
-
     copyFromUTF16(d->data, s.c_str(), s.length(), t);
   }
   else {
@@ -190,17 +187,15 @@ String::String(const wstring &s, Type t) :
   }
 }
 
+String::String(const wchar_t *s) :
+  String(s, wcharByteOrder())
+{
+}
+
 String::String(const wchar_t *s, Type t) :
   d(std::make_shared<StringPrivate>())
 {
   if(t == UTF16 || t == UTF16BE || t == UTF16LE) {
-    // This looks ugly but needed for the compatibility with TagLib1.8.
-    // Should be removed in TabLib2.0.
-    if (t == UTF16BE)
-      t = wcharByteOrder();
-    else if (t == UTF16LE)
-      t = (wcharByteOrder() == UTF16LE ? UTF16BE : UTF16LE);
-
     copyFromUTF16(d->data, s, ::wcslen(s), t);
   }
   else {
diff --git a/taglib/toolkit/tstring.h b/taglib/toolkit/tstring.h
index 4d055428..78abe3ec 100644
--- a/taglib/toolkit/tstring.h
+++ b/taglib/toolkit/tstring.h
@@ -139,22 +139,24 @@ namespace TagLib {
     String(const std::string &s, Type t = Latin1);
 
     /*!
-     * Makes a deep copy of the data in \a s.
-     *
-     * /note If \a t is UTF16LE, the byte order of \a s will be swapped regardless
-     * of the CPU byte order.  If UTF16BE, it will not be swapped.  This behavior
-     * will be changed in TagLib2.0.
+     * Makes a deep copy of the data in \a s, which are in CPU byte order.
      */
-    String(const wstring &s, Type t = UTF16BE);
+    String(const wstring &s);
 
     /*!
-     * Makes a deep copy of the data in \a s.
-     *
-     * /note If \a t is UTF16LE, the byte order of \a s will be swapped regardless
-     * of the CPU byte order.  If UTF16BE, it will not be swapped.  This behavior
-     * will be changed in TagLib2.0.
+     * Makes a deep copy of the data in \a s, which are in byte order \a t.
      */
-    String(const wchar_t *s, Type t = UTF16BE);
+    String(const wstring &s, Type t);
+
+    /*!
+     * Makes a deep copy of the data in \a s, which are in CPU byte order.
+     */
+    String(const wchar_t *s);
+
+    /*!
+     * Makes a deep copy of the data in \a s, which are in byte order \a t.
+     */
+    String(const wchar_t *s, Type t);
 
     /*!
      * Makes a deep copy of the data in \a c.
diff --git a/taglib/toolkit/tutils.h b/taglib/toolkit/tutils.h
index 121c24f6..ee60d386 100644
--- a/taglib/toolkit/tutils.h
+++ b/taglib/toolkit/tutils.h
@@ -203,14 +203,14 @@ namespace TagLib
       /*!
        * Returns the byte order of the system.
        */
-      inline ByteOrder systemByteOrder()
+      constexpr ByteOrder systemByteOrder()
       {
-        union {
+        constexpr union IntCharUnion {
           int  i;
           char c;
-        } u;
+          constexpr IntCharUnion(int j) : i(j) {}
+        } u{1};
 
-        u.i = 1;
         if(u.c == 1)
           return LittleEndian;
         return BigEndian;
diff --git a/tests/test_string.cpp b/tests/test_string.cpp
index 8689c819..a03772f1 100644
--- a/tests/test_string.cpp
+++ b/tests/test_string.cpp
@@ -26,6 +26,7 @@
 #include <cstring>
 
 #include "tstring.h"
+#include "tutils.h"
 #include <cppunit/extensions/HelperMacros.h>
 
 using namespace std;
@@ -96,19 +97,23 @@ public:
     String unicode3(L"\u65E5\u672C\u8A9E");
     CPPUNIT_ASSERT(*(unicode3.toCWString() + 1) == L'\u672C');
 
-    String unicode4(L"\u65e5\u672c\u8a9e", String::UTF16BE);
+    const wchar_t wcSystemOrder[] = {L'\u65E5', L'\u672C', L'\u8A9E', 0};
+    const wchar_t wcSwappedOrder[] = {L'\uE565', L'\u2C67', L'\u9E8A', 0};
+    const std::wstring wsSystemOrder = L"\u65e5\u672c\u8a9e";
+    const std::wstring wsSwappedOrder = L"\ue565\u2c67\u9e8a";
+    const bool isLe = Utils::systemByteOrder() == Utils::LittleEndian;
+
+    String unicode4(isLe ? wcSwappedOrder : wcSystemOrder, String::UTF16BE);
     CPPUNIT_ASSERT(unicode4[1] == L'\u672c');
 
-    String unicode5(L"\u65e5\u672c\u8a9e", String::UTF16LE);
-    CPPUNIT_ASSERT(unicode5[1] == L'\u2c67');
+    String unicode5(isLe ? wcSystemOrder : wcSwappedOrder, String::UTF16LE);
+    CPPUNIT_ASSERT(unicode5[1] == L'\u672c');
 
-    std::wstring stduni = L"\u65e5\u672c\u8a9e";
-
-    String unicode6(stduni, String::UTF16BE);
+    String unicode6(isLe ? wsSwappedOrder : wsSystemOrder, String::UTF16BE);
     CPPUNIT_ASSERT(unicode6[1] == L'\u672c');
 
-    String unicode7(stduni, String::UTF16LE);
-    CPPUNIT_ASSERT(unicode7[1] == L'\u2c67');
+    String unicode7(isLe ? wsSystemOrder : wsSwappedOrder, String::UTF16LE);
+    CPPUNIT_ASSERT(unicode7[1] == L'\u672c');
 
     CPPUNIT_ASSERT(String("  foo  ").stripWhiteSpace() == String("foo"));
     CPPUNIT_ASSERT(String("foo    ").stripWhiteSpace() == String("foo"));