The 30-year-old former Northampton Town striker, who now plays in South Korea, scored with a last-gasp header to mark his return to the national side for the first time in three years.
A second string Ghana side led after a 12th minute penalty converted by Emmanuel Agyemang Badu but Gabon were level on the stroke of half-time through Eric Mouloungui, who headed home a free-kick from Stephane Nguema.
Both sides were preparing for next year's African Nations Cup finals where Gabon are co-hosts and Ghana are among the favourites.
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