Steven Gerrard has urged Rangers supporters to behave in Porto to ensure they have their full backing for the rest of their Europa League campaign.
Ibrox has had 3,000 seats closed off in each of Rangers' last two European games after UEFA sanctioned supporters for sectarian chants in two qualifying matches.
The club declined their ticket allocation for their most recent game, although about 600 fans still found their way into the 2-1 defeat by Young Boys in Switzerland.
Rangers issued a lengthy message to supporters telling them to beware of UEFA actions and Gerrard backed that stance.
"There's nothing better when you can hear the Rangers supporters in full voice getting right behind the team, it's incredible support," the Light Blues manager said.
"They have been with us and helped us immensely over the 16-17 months I have been in the club.
"So we ask for that same support and we echo the message that the club has put out that it's very important they behave in the right way because we don't want to see further punishment further down the line.
"We want Ibrox to be rocking in the two remaining home fixtures with a full house, not sections missing.
"We also want our fans to be able to go over to Feyenoord and be able to enjoy that fixture as well. They have the opportunity to make everybody connected with the club proud of their behaviour."
The club statement earlier read: "The behaviour of our fans in recent times has been exemplary but it is important to maintain those standards at home and abroad.
"At all times we must be aware that whatever we do, both inside and outside the stadium today and tomorrow, our behaviour will come under the closest scrutiny.
"Having said that, however, this fixture also provides another opportunity for Rangers to be showcased as a modern, all-inclusive club.
"Let others fall foul of the authorities – we have seen what happened in Bulgaria just more than a week ago and there is now an investigation into a racist slur against one of our own – while we concentrate on supporting Steven Gerrard and his players in the correct way.
"Be loud and be heard and hopefully celebrate a victory with the team at the end of the match but please, keep in mind that UEFA's view of racism is wide ranging, which means singing or behaviour that could bring much more serious repercussions for the club must be avoided."
