*** a/contrib/postgres_fdw/deparse.c
--- b/contrib/postgres_fdw/deparse.c
***************
*** 253,258 **** foreign_expr_walker(Node *node,
--- 253,268 ----
  				if (var->varno == glob_cxt->foreignrel->relid &&
  					var->varlevelsup == 0)
  				{
+ 					/*
+ 					 * System columns can't be sent to remote since the values
+ 					 * for system columns might be different between local and
+ 					 * remote.
+ 					 *
+ 					 * XXX: we should probably send ctid to remote.
+ 					 */
+ 					if (var->varattno < 0)
+ 						return false;
+ 
  					/* Var belongs to foreign table */
  					collation = var->varcollid;
  					state = OidIsValid(collation) ? FDW_COLLATE_SAFE : FDW_COLLATE_NONE;
***************
*** 1262,1267 **** deparseVar(Var *node, deparse_expr_cxt *context)
--- 1272,1280 ----
  	if (node->varno == context->foreignrel->relid &&
  		node->varlevelsup == 0)
  	{
+ 		/* Var shouldn't be a system column */
+ 		Assert(node->varattno >= 0);
+ 
  		/* Var belongs to foreign table */
  		deparseColumnRef(buf, node->varno, node->varattno, context->root);
  	}
*** a/contrib/postgres_fdw/expected/postgres_fdw.out
--- b/contrib/postgres_fdw/expected/postgres_fdw.out
***************
*** 353,358 **** EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
--- 353,368 ----
     Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" WHERE (("C 1" = c2))
  (3 rows)
  
+ -- where with system column conditions
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.tableoid != 0;
+                                QUERY PLAN                                
+ -------------------------------------------------------------------------
+  Foreign Scan on public.ft1 t1
+    Output: c1, c2, c3, c4, c5, c6, c7, c8
+    Filter: (t1.tableoid <> 0::oid)
+    Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
+ (4 rows)
+ 
  -- ===================================================================
  -- WHERE with remotely-executable conditions
  -- ===================================================================
*** a/contrib/postgres_fdw/sql/postgres_fdw.sql
--- b/contrib/postgres_fdw/sql/postgres_fdw.sql
***************
*** 180,185 **** EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = postgres_fdw_a
--- 180,187 ----
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2;
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = abs(t1.c2);
  EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.c1 = t1.c2;
+ -- where with system column conditions
+ EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 WHERE t1.tableoid != 0;
  
  -- ===================================================================
  -- WHERE with remotely-executable conditions