Undefined Symbols for custom C++ classes in Xcode 4.6.3. Works in Xcode 4.5.2

Undefined Symbols for custom C++ classes in Xcode 4.6.3. Works in Xcode 4.5.2

I have an iOS app that works fine in Xcode 4.5.2 but in Xcode 4.6.3 i get
undefined symbols for my custom c++ classes.
SomeClass.hpp
class SomeClass{
public:
SomeClass();
void doStuff();
}
SomeClass.cpp
#include "SomeClass.hpp"
SomeClass::SomeClass(){
// ra ra ra
}
SomeClass::doStuff() {
// ra ra ra
}
CallingClass.mm
#include "SomeClass.hpp"
@implementation CallingClass
-(void) execute{
SomeClass someObject;
someObject.doStuff();
}
@end
Error
Undefined Symbols for arm7:
SomeClass::SomeClass() referenced from:
-[CallingClass execute:] in CallingClass.o
The .hpp files are set to C++ Headers, the .cpp files are set to C++
Source, and the .mm files are set to Objective-C++ Source. libc++.dylib is
included in the project for a library that i'm using.
Any guidance would be highly appreciated.
Cheers