(Potential bug) Useless warning that shouldn't exist?

[Alec Teal]

Hey guys,

I'm really not sure what's wrong with this, I think it may be a bug but 
I am not sure. Hence posting it here first. These are from a shared 
library, that compiles fine with -Wall -Wextra, the header file is 
available to things that use the library. Particularly this has nothing 
to do with a  function, so why is it talking of a return type of a function?

Header file:
namespace sr {

class Framebuffer;

class Depthbuffer {
public:
*static const float INFINITY;*<--this line is what the warning is 
referring to.
...

Implementation file:
namespace sr {

const float Depthbuffer::INFINITY = 1.0f;
....

However when compiling a program that uses the library:

if ! g++ -Isrc -MM src/Renderer.cpp >> build/Renderer.o.d ; then rm 
build/Renderer.o.d ; exit 1 ; fi
g++ -Wall -Wextra -g -O0 -std=c++0x -gdwarf-2 -Wno-write-strings 
-I../libsr 
-I/usr/lib/x86_64-linux-gnu/wx/include/gtk2-unicode-release-2.8 
-I/usr/include/wx-2.8 -D_FILE_OFFSET_BITS=64 -D_LARGE_FILES -D__WXGTK__ 
-pthread -Isrc -c src/Renderer.cpp -o build/Renderer.o
In file included from ./libsr/libsr.h:12:0,
                  from src/Renderer.h:11,
                  from src/Renderer.cpp:8:
./libsr/Framebuffer.h:17:21: warning: type qualifiers ignored on 
function return type [-Wignored-qualifiers]

The line it doesn't like is the one in bold, static const float INFINITY;

What is GCC warning me about? What's wrong?
GCC 4.7.3

Alec