diff --git a/contrib/hstore/hstore_io.c b/contrib/hstore/hstore_io.c
index 93206193916..cf6fd7c6aa5 100644
--- a/contrib/hstore/hstore_io.c
+++ b/contrib/hstore/hstore_io.c
@@ -339,7 +339,8 @@ hstoreUniquePairs(Pairs *a, int32 l, int32 *buflen)
 		{
 			*buflen += res->keylen + ((res->isnull) ? 0 : res->vallen);
 			res++;
-			memcpy(res, ptr, sizeof(Pairs));
+			if (res != ptr)
+				memcpy(res, ptr, sizeof(Pairs));
 		}
 
 		ptr++;