include_HEADERS and all-am

[jling]

Given my Makefile.am:

AM_CPPFLAGS = -I$(srcdir)/../inc
lib_LIBRARIES = libtest.a
libtest_a_SOURCES = test.cpp test.hpp

This works fine.

Now I add to the end of that:
include_HEADERS = test.hpp

Now I get a make error:

make[2]:  *** No rule to make target 'test.hpp', needed by `all-am'. 
Stop.

Why does make, now consider this a target to make?  I thought 
include_HEADERS just indicates where the header specified should be 
installed, during a "make install".  How do I get around this error?

Thanks,
John