Automake 1.5: Documentation generation

[Sebastian Huber]

Hello,
I used to generate my Doxygen documentation generation this way (Makefile.am):
EXTRA_DIST = @address@hidden

CLEANFILES = *.html *.gif *.css

noinst_PROGRAMS = index.html

index_html_SOURCES = @address@hidden

index.html: @address@hidden
        doxygen @address@hidden

But with the update from 1.4.p5 to 1.5 I am confronted with this error 
message:
doc/Makefile.am:9: deprecated feature: `index.html' overrides 
`index.html$(EXEEXT)'
doc/Makefile.am:9: change your target to read `index.html$(EXEEXT)'

Does anyone know a better way to generate such documentation?

Thanks in advance

Sebastian