sumif between sheets

[Jim Foltz <jimfoltz ald net>]

I posted this thru Google Groups, but it looks like no one has used the
list since last year.

I want to use sumif on Sheet2 to select and sum values from Sheet1, but
all I get is #VALUE!. My function looks like:

=sumif(Sheet1!A1:A5,A1,Sheet1!B1:B5)

Sheet1
A1:Foo B1:1
A2:Bar B2:2
A3:Foo B3:3
A4:Bar B4:4
A5:Baz B5:5

Sheet2
A1:Foo B1:=sumif(Sheet1!A1:A5,A1,Sheet1!B1:B5)

Not sure where the problem is.