PVS-Studio warning V593 for KDE4

void LDAPProtocol::del( const KUrl &_url, bool )
{
  ....
  if ( (id = mOp.del( usrc.dn() ) == -1) ) {
    LDAPErr();
    return;
  }
  ret = mOp.waitForResult( id, -1 );
  ....
}

This suspicious code was found in KDE4 project by PVS-Studio static code analyzer.
Warning message is:
V593 Consider reviewing the expression of the 'A = B == C' kind. The expression is calculated as following: 'A = (B == C)'. kio_ldap.cpp 535

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