Funny error in GNUmake 3.80

[Yuri Shtil]

Here is a simple Makefile that illustrates a problem I encountered:

--------------------------------------------------
define FUNCTION
$(1) : $(2)
 @echo Making $$@ from $$?
$(2) :
 @echo Making $$@
endef

ifdef BLA

$(eval $(call FUNCTION,a,b))

endif
-----------------------------------------------

If I invoke make on this file not defining BLA, I get make: *** No targets.
Stop.
This is expected.

If I say:

make BLA=yes, I get an error
Makefile:9: *** missing `endif'.  Stop.

If I remove ifdef BLA and endif around $(eval) and call make, then I get as
expected.

Making b
Making a from b

Anybody any clue?