diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index fac395f..486c2e0 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -1970,6 +1970,9 @@
 The leftmost iterators are in the outermost for-loop, so the output tuples\n\
 cycle in a manner similar to an odometer (with the rightmost element changing\n\
 on every iteration).\n\n\
+To compute the product of an iterable with itself, specify the number\n\
+of repetitions with the optional repeat keyword argument. For example,\n\
+product(A, repeat=4) means the same as product(A, A, A, A).\n\n\
 product('ab', range(3)) --> ('a',0) ('a',1) ('a',2) ('b',0) ('b',1) ('b',2)\n\
 product((0,1), (0,1), (0,1)) --> (0,0,0) (0,0,1) (0,1,0) (0,1,1) (1,0,0) ...");