diff --git a/.gitignore b/.gitignore
index 629e360a22..a92b770d60 100644
--- a/.gitignore
+++ b/.gitignore
@@ -56,6 +56,7 @@ profile
 **/doxygen/doc
 **/doxygen/build
 **/.idea
+**/out/build
 extras/Projucer/JUCECompileEngine.dylib
 
 .idea
diff --git a/modules/juce_core/text/juce_String.cpp b/modules/juce_core/text/juce_String.cpp
index 8ac68ea1f1..5c2b3c98fa 100644
--- a/modules/juce_core/text/juce_String.cpp
+++ b/modules/juce_core/text/juce_String.cpp
@@ -255,6 +255,8 @@ String::~String() noexcept
 String::String (const String& other) noexcept   : text (other.text)
 {
     StringHolderUtils::retain (text);
+    size_t num = getNumBytesAsUTF8();
+    preallocateBytes (num);
 }
 
 void String::swapWith (String& other) noexcept
@@ -749,19 +751,30 @@ void String::appendCharPointer (const CharPointerType startOfTextToAppend,
 {
     jassert (startOfTextToAppend.getAddress() != nullptr && endOfTextToAppend.getAddress() != nullptr);
 
-    auto extraBytesNeeded = getAddressDifference (endOfTextToAppend.getAddress(),
-                                                  startOfTextToAppend.getAddress());
-    jassert (extraBytesNeeded >= 0);
 
+    auto bytesNeededForNewPart = getAddressDifference (endOfTextToAppend.getAddress(),
+                                                  startOfTextToAppend.getAddress());
+    jassert (bytesNeededForNewPart >= 0);
+    if (bytesNeededForNewPart == 0) return;
+
+    
+    auto allocatedNumBytes = StringHolderUtils::getAllocatedNumBytes (text);
+    auto usedBytes = CharPointerType::getBytesRequiredFor (text) + 1;
+    auto currentlyUnusedBytes = allocatedNumBytes - usedBytes;
+
+    size_t extraBytesNeeded = 0;
+    if (bytesNeededForNewPart > currentlyUnusedBytes)
+        extraBytesNeeded = bytesNeededForNewPart - currentlyUnusedBytes;
+
+    auto byteOffsetOfNull = getByteOffsetOfEnd();
     if (extraBytesNeeded > 0)
     {
-        auto byteOffsetOfNull = getByteOffsetOfEnd();
-        preallocateBytes ((size_t) extraBytesNeeded + byteOffsetOfNull);
-
-        auto* newStringStart = addBytesToPointer (text.getAddress(), (int) byteOffsetOfNull);
-        memcpy (newStringStart, startOfTextToAppend.getAddress(), (size_t) extraBytesNeeded);
-        CharPointerType (addBytesToPointer (newStringStart, extraBytesNeeded)).writeNull();
+        preallocateBytes(extraBytesNeeded + allocatedNumBytes + 1);
     }
+
+    auto* newStringStart = addBytesToPointer (text.getAddress(), (int)byteOffsetOfNull);
+    memcpy (newStringStart, startOfTextToAppend.getAddress(), (size_t) bytesNeededForNewPart);
+    CharPointerType (addBytesToPointer (newStringStart, bytesNeededForNewPart)).writeNull();
 }
 
 String& String::operator+= (const wchar_t* t)
@@ -845,17 +858,17 @@ JUCE_API String JUCE_CALLTYPE operator+ (const wchar_t* s1, const String& s2) {
 JUCE_API String JUCE_CALLTYPE operator+ (char s1, const String& s2)           { return String::charToString ((juce_wchar) (uint8) s1) + s2; }
 JUCE_API String JUCE_CALLTYPE operator+ (wchar_t s1, const String& s2)        { return String::charToString (s1) + s2; }
 
-JUCE_API String JUCE_CALLTYPE operator+ (String s1, const String& s2)         { return s1 += s2; }
-JUCE_API String JUCE_CALLTYPE operator+ (String s1, const char* s2)           { return s1 += s2; }
-JUCE_API String JUCE_CALLTYPE operator+ (String s1, const wchar_t* s2)        { return s1 += s2; }
-JUCE_API String JUCE_CALLTYPE operator+ (String s1, const std::string& s2)    { return s1 += s2.c_str(); }
+JUCE_API String JUCE_CALLTYPE operator+ (String s1, const String& s2)         { String s(s1); return s += s2; }
+JUCE_API String JUCE_CALLTYPE operator+ (String s1, const char* s2)           { String s(s1); return s += s2; }
+JUCE_API String JUCE_CALLTYPE operator+ (String s1, const wchar_t* s2)        { String s(s1); return s += s2; }
+JUCE_API String JUCE_CALLTYPE operator+ (String s1, const std::string& s2)    { String s(s1); return s += s2.c_str(); }
 
-JUCE_API String JUCE_CALLTYPE operator+ (String s1, char s2)                  { return s1 += s2; }
-JUCE_API String JUCE_CALLTYPE operator+ (String s1, wchar_t s2)               { return s1 += s2; }
+JUCE_API String JUCE_CALLTYPE operator+ (String s1, char s2)                  { String s(s1); return s += s2; }
+JUCE_API String JUCE_CALLTYPE operator+ (String s1, wchar_t s2)               { String s(s1); return s += s2; }
 
 #if ! JUCE_NATIVE_WCHAR_IS_UTF32
 JUCE_API String JUCE_CALLTYPE operator+ (juce_wchar s1, const String& s2)     { return String::charToString (s1) + s2; }
-JUCE_API String JUCE_CALLTYPE operator+ (String s1, juce_wchar s2)            { return s1 += s2; }
+JUCE_API String JUCE_CALLTYPE operator+ (String s1, juce_wchar s2)            { String s(s1); return s += s2; }
 JUCE_API String& JUCE_CALLTYPE operator<< (String& s1, juce_wchar s2)         { return s1 += s2; }
 #endif
 
@@ -2509,6 +2522,11 @@ public:
             s2 << StringRef ("def");
             expect (s2 == "1234567890xyz123123def");
 
+            String sPrealloc ("a");
+            sPrealloc.preallocateBytes (10);
+            sPrealloc += "bcd";
+            expect (sPrealloc == "abcd");
+
             // int16
             {
                 String numStr (std::numeric_limits<int16>::max());