glext.h not matching spec?

I’ve encountered a little problem initialising ARB_instanced_arrays. The spec file says

void VertexAttribDivisorARB(uint index, uint divisor);

so I expected that “PFNGLVERTEXATTRIBDIVISORARBPROC glVertexAttribDivisorARB;” would be the right thing to do.
However, this fails to compile, and looking into glext.h (most recent version downloaded from reveals why: the function pointer typedef name is PFNGLVERTEXATTRIBDIVISORPROC (no “ARB”). The corresponding prototype, too, lacks the ARB suffix. The same seems to be the case for a few other extensions.

Is there something that I don’t understand properly, or is there a discrepancy between specs and glext.h?

Sometimes errors creep into glext.h. Make sure you are using the latest version from the registry.