Various Liquid string filters not working

Using jekyll 2.2.0 and liquid 2.6.1
```
{{ "hello" | slice: 2 }}
{{ "hello" | slice: 1, 3 }}
{{ "hello" | slice: -3, 2  }}
```
should yield:
```
e
ell
el
```
but instead yields: 
```
hello
hello
hello
```
also
```
{{ '   too many spaces      ' | strip }}
{{ '   too many spaces           ' | lstrip }}
{{ '              too many spaces      ' | rstrip }}
```
should yield:
```
too many spaces
too many spaces           
              too many spaces
```
but instead yields: 
```
   too many spaces      
   too many spaces           
              too many spaces      
```
Same with jekyll 2.3.0.  

Am I missing something?