Hopper lock doesn't work

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What I expected to happen was:
When player put items in locked hopper and there is hopper below items stay in first hopper
 
What actually happened was...:
When player put items in locked hopper and there is hopper below items go to second hopper
 
Steps to Reproduce:
1. Place two hoppers vertically and lock them with redstone.
2. Put items in first hopper.
3. Notice that items are going to second hopper.
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