diff --git a/contrib/seg/seg.c b/contrib/seg/seg.c
index 930a35b0093..0a6cd025293 100644
--- a/contrib/seg/seg.c
+++ b/contrib/seg/seg.c
@@ -432,7 +432,7 @@ gseg_picksplit(GistEntryVector *entryvec,
 		else
 		{
 			datum_r = union_dr;
-			size_r = size_alpha;
+			size_r = size_beta;
 			*right++ = i;
 			v->spl_nright++;
 		}