PVS-Studio warning V559 for Miranda IM

int FindItem(....)
{
  ...
  int ret;
  ret=FindItem(hwnd,dat,hItem,
               (struct ClcContact ** )&z,
               (struct  ClcGroup** )&isv,NULL);
  if (ret=0) {return (0);}
  ...
}

This is what should have been written here: if (ret==0) {return (0);}

This suspicious code was found in Miranda IM project by PVS-Studio static code analyzer.
Warning message is:
V559 Suspicious assignment inside the condition expression of 'if' operator: ret = 0. clist_mw clcidents.c 179

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/