diff --git a/src/test/modules/test_bitmapset/test_bitmapset.c b/src/test/modules/test_bitmapset/test_bitmapset.c
index 8bc9b1f48e..9e757732c5 100644
--- a/src/test/modules/test_bitmapset/test_bitmapset.c
+++ b/src/test/modules/test_bitmapset/test_bitmapset.c
@@ -700,7 +700,8 @@ test_random_operations(PG_FUNCTION_ARGS)
 			case 2:				/* test membership */
 				if (bms != NULL)
 				{
-					bms_is_member(member, bms);
+					if (!bms_is_member(member, bms))
+						elog(ERROR, "union missing member %d", member);
 				}
 				break;
 		}