Design issue

Hi all!

I've got something of a design issue here:

class Bucket {
    public:
        // Initial capacity of a bucket (= # of items in a page)
        static const unsigned int M = 10;

        // Key store
        Key keyStore[M];

        // Count of items in the bucket
        int count;

        // Bucket's depth (number of significant bits)
        int localDepth;

        Bucket();
        ~Bucket();
};

Now, I use Bucket in a data structure like this:

#include "Bucket.h"

Foobar::Foobar() : a(0), b(0), c(0) {
}

void Foobar buzz() {
    if(Bucket::M < 1)
        ...
}

Although this compiles just fine, if I want to use it e.g. write
something like

#include "Foobar.h"
int maint() {
   Foobar* b = new Foobar();
}

I get a "undefined reference" from ld. Googling on this I found out
that I have one has to initialize a static variable in exactly one
compilation unit (see [10.10] Why can't I initialize my static member
data in my constructor's initialization list? by Marshall Cline).
But how do I fix this?

Thanks in advance,
Philipp