# \allowdisplaybreaks does not work anymore if empheq is loaded

I'm using the package mathtools using the option showonlyrefs. This works fine, however some equation numbers are skipped. If I understood the manual correctly I need to load empheq to fix this. This works!

The problem now is that without empheq \allowdisplaybreaks works fine, but the equation numbering goes wrong, but with empheq the \allowdisplaybreaks seems to stop working (this is a command from amsmath).

Is this a common problem? I can't seem to find anything about it. How can I solve this?

Edit: I have finally found the time to make a MWE. See below.

\documentclass[a4paper,10pt, leqno, final, twoside]{scrbook}
\usepackage{amsmath}
\usepackage[amsmath, thmmarks]{ntheorem}
\allowdisplaybreaks[4]
\usepackage{mathtools}
\mathtoolsset{showonlyrefs}
\mathtoolsset{showonlyrefs,showmanualtags}
\newtagform{brackets}{[}{]}
\usetagform{brackets}
\usepackage{blindtext}

\begin{document}

\blindtext[3]
\begin{align}
A &= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A\\
&= A
\end{align}

\end{document}

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Could you add a minimal working example (MWE) that illustrates the problem? –  Karl Ove Hufthammer Nov 2 '11 at 16:03
I tried with a simple document, with no problem. –  egreg Nov 2 '11 at 16:49
Okay, then I will add a MWE soon. –  Jonas Teuwen Nov 2 '11 at 16:58

Drop the overload option for the empheq package. You then can't use the short form for emphasized equations. See Section 2.2.2 of the package manual.

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Thanks. That does fix a lot. However, now for some reason \tag[$\ast$] stopped working. Could this be connected to this? –  Jonas Teuwen Nov 10 '11 at 10:47
Shouldn't that read \tag{$\ast$}? –  Thorsten Donig Nov 10 '11 at 10:55
Yes, that's correct. –  Jonas Teuwen Nov 10 '11 at 11:44
I have no problem with manual tagging. –  Thorsten Donig Nov 10 '11 at 11:50
It is a strange thing, sometimes \tag{$\ast$} doesn't work, sometimes it does and when it doesn't \tag{*} does work. I'll try to figure out. –  Jonas Teuwen Nov 10 '11 at 11:58