diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index fafbab6b02..b40c331f8f 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -7185,6 +7185,10 @@ make_tuple_from_result_row(PGresult *res,
 /*
  * Callback function which is called when error occurs during column value
  * conversion.  Print names of column and relation.
+ *
+ * Note that this function mustn't do any catalog lookups, since we are in
+ * an already-failed transaction.  Fortunately, we can get info from the
+ * relcache entry (for a simple scan) or the query rangetable (for joins).
  */
 static void
 conversion_error_callback(void *arg)
@@ -7198,10 +7202,14 @@ conversion_error_callback(void *arg)
 	{
 		/* error occurred in a scan against a foreign table */
 		TupleDesc	tupdesc = RelationGetDescr(errpos->rel);
-		Form_pg_attribute attr = TupleDescAttr(tupdesc, errpos->cur_attno - 1);
 
 		if (errpos->cur_attno > 0 && errpos->cur_attno <= tupdesc->natts)
+		{
+			Form_pg_attribute attr = TupleDescAttr(tupdesc,
+												   errpos->cur_attno - 1);
+
 			attname = NameStr(attr->attname);
+		}
 		else if (errpos->cur_attno == SelfItemPointerAttributeNumber)
 			attname = "ctid";
 
@@ -7220,35 +7228,32 @@ conversion_error_callback(void *arg)
 
 		/*
 		 * Target list can have Vars and expressions.  For Vars, we can get
-		 * its relation, however for expressions we can't.  Thus for
+		 * some information, however for expressions we can't.  Thus for
 		 * expressions, just show generic context message.
 		 */
 		if (IsA(tle->expr, Var))
 		{
-			RangeTblEntry *rte;
 			Var		   *var = (Var *) tle->expr;
+			RangeTblEntry *rte = exec_rt_fetch(var->varno, estate);
 
-			rte = exec_rt_fetch(var->varno, estate);
+			relname = rte->eref->aliasname;
 
 			if (var->varattno == 0)
 				is_wholerow = true;
-			else
-				attname = get_attname(rte->relid, var->varattno, false);
-
-			relname = get_rel_name(rte->relid);
+			else if (var->varattno > 0 &&
+					 var->varattno <= list_length(rte->eref->colnames))
+				attname = strVal(list_nth(rte->eref->colnames,
+										  var->varattno - 1));
 		}
-		else
-			errcontext("processing expression at position %d in select list",
-					   errpos->cur_attno);
 	}
 
-	if (relname)
-	{
-		if (is_wholerow)
-			errcontext("whole-row reference to foreign table \"%s\"", relname);
-		else if (attname)
-			errcontext("column \"%s\" of foreign table \"%s\"", attname, relname);
-	}
+	if (relname && is_wholerow)
+		errcontext("whole-row reference to foreign table \"%s\"", relname);
+	else if (relname && attname)
+		errcontext("column \"%s\" of foreign table \"%s\"", attname, relname);
+	else
+		errcontext("processing expression at position %d in select list",
+				   errpos->cur_attno);
 }
 
 /*