Assertion failure in indxpath.c

I'm getting an assertion failure on a fresh git checkout with this query:

create table foo (a int4, b text);CREATE TABLE
create index i_foo on foo (b, a);CREATE INDEX
select * from foo where a = 0 and (b = 'foo' or b = 'bar');

TRAP: FailedAssertion("!(((((const Node*)(ipath))->type) == 
T_IndexPath))", File: "indxpath.c", Line: 1328)

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com