The Washington State Department of Transportation has a problem that just won’t go away.

For years, people have persistently stolen those green and white mile markers posted along the highway. The most popular signs to pilfer are Mile 420, a popular number among marijuana enthusiasts, and Mile, ahem, 69. (If you don’t know that one by now, we can’t help you.)

“They will typically go and take those more than anything,” said Trevor McCain, who specializes in driver information signs at the Transportation Department. “They have special meanings to some people.”

So the sign aficionados in Washington had to get creative. In hot spots for sign theft, they’ve simply moved the highway marker back one-tenth of a mile and tweaked the sign to say Mile 419.9. Or Mile 68.9.