Leaves replace transparent blocks

Put the summary of the bug you're having here

What I expected to happen was...:
When a jungle tree was grown from a sapling, I expected it to avoid replacing solid blocks, including walls.

What actually happened was...:
I had the trees in a deep pit surrounded by a mossy cobblestone walkway and mossy cobblestone wall for aesthetics; a segment of the wall at the top was replaced by leaf blocks.

Steps to Reproduce:
1. Plant a jungle or birch tree
2. Place mossy cobblestone (or presumably also cobblestone) wall close to the sapling and above, at leaf-height).
3. Wait for it to grow or use bonemeal.