Clear signs

When I place signs, type in, and exit, the sign is clear. Even after I exit the world and come back on, its still there. It now happens on others worlds also.

What I expected:
The sign should be wooden.

What happened:
The sign is clear, but still has text on it. The base of the sign remains normal though.

Steps:
1.Place sign
2. Type in whatever
3.Then there, you have it.