Water and Lava do Not Mix to Create Obsidian

Put the summary of the bug you're having here

What I expected to happen was...:
1) Right-clicking with a Lava Bucket in my main hand creates an Obsidian Block when placed onto a space occupied by Water.

2) Right-clicking with a Water Bucket in my main hand creates an Obsidian Block when placed onto a space occupied by Lava.

What actually happened was...:
1) Right-clicking with a Lava Bucket in my main hand replaces a Water source block with a Lava source block.

2) Right-clicking with a Water Bucket in my main hand replaces Lava source block with a Water source block.

Steps to Reproduce:
1. Empty either a water or lava bucket onto a block of the opposite liquid.