diff --git a/src/backend/access/common/tupdesc.c b/src/backend/access/common/tupdesc.c
index d771a265b34..196472c05d0 100644
--- a/src/backend/access/common/tupdesc.c
+++ b/src/backend/access/common/tupdesc.c
@@ -246,10 +246,11 @@ CreateTupleDescCopy(TupleDesc tupdesc)
 
 	desc = CreateTemplateTupleDesc(tupdesc->natts);
 
-	/* Flat-copy the attribute array */
-	memcpy(TupleDescAttr(desc, 0),
-		   TupleDescAttr(tupdesc, 0),
-		   desc->natts * sizeof(FormData_pg_attribute));
+	/* Flat-copy the attribute array (unless there are no attributes) */
+	if (desc->natts > 0)
+		memcpy(TupleDescAttr(desc, 0),
+			   TupleDescAttr(tupdesc, 0),
+			   desc->natts * sizeof(FormData_pg_attribute));
 
 	/*
 	 * Since we're not copying constraints and defaults, clear fields
@@ -294,10 +295,11 @@ CreateTupleDescTruncatedCopy(TupleDesc tupdesc, int natts)
 
 	desc = CreateTemplateTupleDesc(natts);
 
-	/* Flat-copy the attribute array */
-	memcpy(TupleDescAttr(desc, 0),
-		   TupleDescAttr(tupdesc, 0),
-		   desc->natts * sizeof(FormData_pg_attribute));
+	/* Flat-copy the attribute array (unless there are no attributes) */
+	if (desc->natts > 0)
+		memcpy(TupleDescAttr(desc, 0),
+			   TupleDescAttr(tupdesc, 0),
+			   desc->natts * sizeof(FormData_pg_attribute));
 
 	/*
 	 * Since we're not copying constraints and defaults, clear fields
@@ -339,10 +341,11 @@ CreateTupleDescCopyConstr(TupleDesc tupdesc)
 
 	desc = CreateTemplateTupleDesc(tupdesc->natts);
 
-	/* Flat-copy the attribute array */
-	memcpy(TupleDescAttr(desc, 0),
-		   TupleDescAttr(tupdesc, 0),
-		   desc->natts * sizeof(FormData_pg_attribute));
+	/* Flat-copy the attribute array (unless there are no attributes) */
+	if (desc->natts > 0)
+		memcpy(TupleDescAttr(desc, 0),
+			   TupleDescAttr(tupdesc, 0),
+			   desc->natts * sizeof(FormData_pg_attribute));
 
 	for (i = 0; i < desc->natts; i++)
 	{
diff --git a/src/include/access/tupdesc.h b/src/include/access/tupdesc.h
index 62ef6b38497..d26287271e9 100644
--- a/src/include/access/tupdesc.h
+++ b/src/include/access/tupdesc.h
@@ -179,6 +179,8 @@ TupleDescAttr(TupleDesc tupdesc, int i)
 {
 	FormData_pg_attribute *attrs = TupleDescAttrAddress(tupdesc);
 
+	Assert(i >= 0 && i < tupdesc->natts);
+
 	return &attrs[i];
 }
 
diff --git a/src/pl/plperl/plperl.c b/src/pl/plperl/plperl.c
index c5f11b874c7..06ebffa111c 100644
--- a/src/pl/plperl/plperl.c
+++ b/src/pl/plperl/plperl.c
@@ -1093,7 +1093,7 @@ plperl_build_tuple_result(HV *perlhash, TupleDesc td)
 		SV		   *val = HeVAL(he);
 		char	   *key = hek2cstr(he);
 		int			attn = SPI_fnumber(td, key);
-		Form_pg_attribute attr = TupleDescAttr(td, attn - 1);
+		Form_pg_attribute attr;
 
 		if (attn == SPI_ERROR_NOATTRIBUTE)
 			ereport(ERROR,
@@ -1106,6 +1106,7 @@ plperl_build_tuple_result(HV *perlhash, TupleDesc td)
 					 errmsg("cannot set system attribute \"%s\"",
 							key)));
 
+		attr = TupleDescAttr(td, attn - 1);
 		values[attn - 1] = plperl_sv_to_datum(val,
 											  attr->atttypid,
 											  attr->atttypmod,
@@ -1799,7 +1800,7 @@ plperl_modify_tuple(HV *hvTD, TriggerData *tdata, HeapTuple otup)
 		char	   *key = hek2cstr(he);
 		SV		   *val = HeVAL(he);
 		int			attn = SPI_fnumber(tupdesc, key);
-		Form_pg_attribute attr = TupleDescAttr(tupdesc, attn - 1);
+		Form_pg_attribute attr;
 
 		if (attn == SPI_ERROR_NOATTRIBUTE)
 			ereport(ERROR,
@@ -1811,6 +1812,8 @@ plperl_modify_tuple(HV *hvTD, TriggerData *tdata, HeapTuple otup)
 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 					 errmsg("cannot set system attribute \"%s\"",
 							key)));
+
+		attr = TupleDescAttr(tupdesc, attn - 1);
 		if (attr->attgenerated)
 			ereport(ERROR,
 					(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index 45d667428f4..65b0fd0790f 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -3401,7 +3401,7 @@ exec_stmt_return_next(PLpgSQL_execstate *estate,
 					PLpgSQL_var *var = (PLpgSQL_var *) retvar;
 					Datum		retval = var->value;
 					bool		isNull = var->isnull;
-					Form_pg_attribute attr = TupleDescAttr(tupdesc, 0);
+					Form_pg_attribute attr;
 
 					if (natts != 1)
 						ereport(ERROR,
@@ -3414,6 +3414,7 @@ exec_stmt_return_next(PLpgSQL_execstate *estate,
 														var->datatype->typlen);
 
 					/* coerce type if needed */
+					attr = TupleDescAttr(tupdesc, 0);
 					retval = exec_cast_value(estate,
 											 retval,
 											 &isNull,
@@ -3532,7 +3533,7 @@ exec_stmt_return_next(PLpgSQL_execstate *estate,
 		}
 		else
 		{
-			Form_pg_attribute attr = TupleDescAttr(tupdesc, 0);
+			Form_pg_attribute attr;
 
 			/* Simple scalar result */
 			if (natts != 1)
@@ -3541,6 +3542,7 @@ exec_stmt_return_next(PLpgSQL_execstate *estate,
 						 errmsg("wrong result type supplied in RETURN NEXT")));
 
 			/* coerce type if needed */
+			attr = TupleDescAttr(tupdesc, 0);
 			retval = exec_cast_value(estate,
 									 retval,
 									 &isNull,