Some players prefer to open 1♦ holding 5 clubs and 4 diamonds to prepare a rebid. This often leads to a false preference for diamonds. For example, if North opens 1♦ with ♠72 ♥96 ♦KQ63 ♣AKJ94, the auction may proceed as shown below.
South, with a hand like ♠QJ854 ♥J93 ♦872 ♣Q72, will take a preference for diamonds. East-West miss their 8-card club fit. North can avoid this by opening 1♣, planning to rebid 1NT or 2♣.
For a great discussion on this topic, see Andrew Gumperz' "4 Diamonds and 5 Clubs" article.
When a minimum opener has an awkward rebid problem, sometimes it is better to pass. See Steve Weinstein's "Let's Take a Pass" article.