 <p>You seem to be writing a makefile in GNUMake style, but actually running some other version of Make. If it's not obvious what autoreconf is calling, you could insert a rule in the makefile:</p> <pre><code>dummy: @echo using $(MAKE) $(MAKE) -v </code></pre> <p>If this theory proves correct, you can either persuade autoconf to use GNUMake, or write for the version it's using.</p>