[make] == unexpected operator

[MaciekL]

Hi,

i have a question abou [make],

/> cat Makefile:
---
.PHONY: all
all:
<tab>if [ "a" == "b" ]; then\
<tab>  echo banan;\
<tab>fi
---

/> make
---
if [ "a" == "b" ]; then\
          echo banan;\
        fi
[: 2: a: unexpected operator
---

What is that (unexpected operator) ?

OS:
Linux xxx 2.6.31-19-generic #56-Ubuntu SMP Thu Jan 28 01:26:53 UTC 2010
i686 GNU/Linux

MAKE:
GNU Make 3.81
Copyright (C) 2006  Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
This program built for i686-redhat-linux-gnu

Any idea ?

-- 
Maciek