Help finding what's causing a semi-hang

Hey guys,
I’ve just found some really strange (and irritating) behaviour: when both IndexedTables and DataFrames are using-ed, IndexedTables.table() takes like 5 minutes to run if a certain argument is passed. To reproduce:

using DataFrames
using IndexedTables
# this is fine
IndexedTables.table((a = ['a', 'b', 'c'], b=[1,2,3]))
# semi-hang here, can't use Ctrl+C to get a stacktrace, takes about 5 minutes on my machine
IndexedTables.table((a = ['a', 'b', 'c'], b=[1,2,3]), pkey=(:a,))

If DataFrames is not imported then it works fine.
I am suspecting compiler fickleness but I don’t really know enough to look into it. Any pointers on debugging this? Tried with 1.4.0 and 1.5.0-rc2.