What may cause zlib decompression to fail?

I am trying to analyze HTTP traffic where the HTTP body is zlib encoded. The packet details pane shows:

Hypertext Transfer Protocol
    POST /xxs/ HTTP/1.1\r\n
    Content-Type: text/xml; charset="utf-8"\r\n
    SOAPAction: \r\n
    Content-Encoding: zlib\r\n
    Text-Length: 550\r\n
    Content-Length: 312\r\n
    Connection: Close\r\n
    \r\n
    Content-encoded entity body (zlib): 312 bytes [Error: Decompression failed]
        Data (312 bytes)

So for some reason the decompression of the zlip compressed data is failing. When I export the raw bytes of the HTTP body to a file I can successfully decompress them with a command line tool (openssl zlib -d). That tells me the content is in fact validly zlib encoded.

What may be causing the zlib decompression to fail in Wireshark? Is there anything further I could try to do to get this to work?

The problem occurs both in

• the current version 1.8.5 (SVN Rev 47350 from /trunk-1.8) on Windows 7 (zlib1.dll is present in Wireshark folder)
• Version 1.2.15 on CentOS (the only version I was able to get hold of on Linux right now)