PL/pgSQL return value in after triggers

diff --git i/doc/src/sgml/plpgsql.sgml w/doc/src/sgml/plpgsql.sgml
index f33cef5..203cb29 100644
--- i/doc/src/sgml/plpgsql.sgml
+++ w/doc/src/sgml/plpgsql.sgml
@@ -1559,7 +1559,7 @@ END;
      <title><command>RETURN</></title>
 
 <synopsis>
-RETURN <replaceable>expression</replaceable>;
+RETURN <optional> <replaceable>expression</replaceable> </optional>;
 </synopsis>
 
      <para>
@@ -1592,6 +1592,13 @@ RETURN <replaceable>expression</replaceable>;
      </para>
 
      <para>
+      A trigger function used in an <literal>AFTER</literal> row trigger or in
+      a statement trigger can also use <command>RETURN</command> without
+      expression.  (The result of any supplied expression would be ignored.)
+      See <xref linkend="plpgsql-trigger"> for details.
+     </para>
+
+     <para>
       The return value of a function cannot be left undefined. If
       control reaches the end of the top-level block of the function
       without hitting a <command>RETURN</command> statement, a run-time
@@ -3511,9 +3518,9 @@ RAISE unique_violation USING MESSAGE = 'Duplicate user ID: ' || user_id;
   </para>
 
    <para>
-    A trigger function must return either <symbol>NULL</symbol> or a
+    A trigger function can return either <symbol>NULL</symbol> or a
     record/row value having exactly the structure of the table the
-    trigger was fired for.
+    trigger was fired for, as follows.
    </para>
 
    <para>
@@ -3558,11 +3565,17 @@ RAISE unique_violation USING MESSAGE = 'Duplicate user ID: ' || user_id;
    </para>
 
    <para>
-    The return value of a row-level trigger
-    fired <literal>AFTER</literal> or a statement-level trigger
-    fired <literal>BEFORE</> or <literal>AFTER</> is
-    always ignored; it might as well be null. However, any of these types of
-    triggers might still abort the entire operation by raising an error.
+    The return value of a row-level trigger fired <literal>AFTER</literal> or a
+    statement-level trigger fired <literal>BEFORE</> or <literal>AFTER</> is
+    always ignored.  In these cases, the <literal>RETURN</literal> statement
+    can be used without argument or omitted altogether.  (A trigger function
+    that is intended to be used in an <literal>AFTER</literal> trigger or a
+    statement-level trigger and supplies a return value that is ignored would
+    misbehave, possibly silently, if accidentally used in
+    a <literal>BEFORE</literal> or <literal>INSTEAD OF</literal> row-level
+    trigger.  So it might be better not to supply a dummy return value.)
+    However, any of these types of triggers might still abort the entire
+    operation by raising an error.
    </para>
 
    <para>
@@ -3655,15 +3668,11 @@ CREATE OR REPLACE FUNCTION process_emp_audit() RETURNS TRIGGER AS $emp_audit$
         --
         IF (TG_OP = 'DELETE') THEN
             INSERT INTO emp_audit SELECT 'D', now(), user, OLD.*;
-            RETURN OLD;
         ELSIF (TG_OP = 'UPDATE') THEN
             INSERT INTO emp_audit SELECT 'U', now(), user, NEW.*;
-            RETURN NEW;
         ELSIF (TG_OP = 'INSERT') THEN
             INSERT INTO emp_audit SELECT 'I', now(), user, NEW.*;
-            RETURN NEW;
         END IF;
-        RETURN NULL; -- result is ignored since this is an AFTER trigger
     END;
 $emp_audit$ LANGUAGE plpgsql;
 
@@ -3885,9 +3894,6 @@ AS $maint_sales_summary_bytime$
                     -- do nothing
             END;
         END LOOP insert_update;
-
-        RETURN NULL;
-
     END;
 $maint_sales_summary_bytime$ LANGUAGE plpgsql;
 
diff --git i/src/pl/plpgsql/src/gram.y w/src/pl/plpgsql/src/gram.y
index 8c4c2f7..a7adb5c 100644
--- i/src/pl/plpgsql/src/gram.y
+++ w/src/pl/plpgsql/src/gram.y
@@ -2868,6 +2868,8 @@ make_return_stmt(int location)
 	}
 	else if (plpgsql_curr_compile->fn_retistuple)
 	{
+		bool saw_semicolon = false;
+
 		switch (yylex())
 		{
 			case K_NULL:
@@ -2885,6 +2887,16 @@ make_return_stmt(int location)
 							 parser_errposition(yylloc)));
 				break;
 
+			case ';':
+				if (plpgsql_curr_compile->fn_is_trigger)
+					saw_semicolon = true;
+				else
+					ereport(ERROR,
+							(errcode(ERRCODE_DATATYPE_MISMATCH),
+							 errmsg("RETURN must specify a record or row variable in function returning row"),
+							 parser_errposition(yylloc)));
+				break;
+
 			default:
 				ereport(ERROR,
 						(errcode(ERRCODE_DATATYPE_MISMATCH),
@@ -2892,7 +2904,7 @@ make_return_stmt(int location)
 						 parser_errposition(yylloc)));
 				break;
 		}
-		if (yylex() != ';')
+		if (!saw_semicolon && yylex() != ';')
 			yyerror("syntax error");
 	}
 	else
diff --git i/src/pl/plpgsql/src/pl_exec.c w/src/pl/plpgsql/src/pl_exec.c
index 717ad79..2236f72 100644
--- i/src/pl/plpgsql/src/pl_exec.c
+++ w/src/pl/plpgsql/src/pl_exec.c
@@ -701,10 +701,11 @@ plpgsql_exec_trigger(PLpgSQL_function *func,
 			ereport(ERROR,
 					(errcode(ERRCODE_SYNTAX_ERROR),
 					 errmsg("CONTINUE cannot be used outside a loop")));
-		else
+		else if (!(TRIGGER_FIRED_FOR_STATEMENT(trigdata->tg_event) || TRIGGER_FIRED_AFTER(trigdata->tg_event)))
 			ereport(ERROR,
 			   (errcode(ERRCODE_S_R_E_FUNCTION_EXECUTED_NO_RETURN_STATEMENT),
-				errmsg("control reached end of trigger procedure without RETURN")));
+				errmsg("control reached end of trigger procedure without RETURN"),
+				errdetail("A trigger procedure used in a row-level trigger that is not fired AFTER must return a value.")));
 	}
 
 	estate.err_stmt = NULL;
diff --git i/src/test/regress/expected/plpgsql.out w/src/test/regress/expected/plpgsql.out
index 238bf5f..cda9928 100644
--- i/src/test/regress/expected/plpgsql.out
+++ w/src/test/regress/expected/plpgsql.out
@@ -4571,3 +4571,49 @@ ERROR:  value for domain orderedarray violates check constraint "sorted"
 CONTEXT:  PL/pgSQL function "testoa" line 5 at assignment
 drop function arrayassign1();
 drop function testoa(x1 int, x2 int, x3 int);
+--
+-- Additional triggers tests
+--
+create table test_triggers (a int, b text);
+-- trigger function without return statement
+create function say_something() returns trigger
+language plpgsql as $$
+begin
+    raise notice '%', tg_argv[0];
+end$$;
+-- trigger function with RETURN without argument
+create function say_something2() returns trigger
+language plpgsql as $$
+begin
+    raise notice '%', tg_argv[0];
+    return;
+end$$;
+create trigger say_hello_s before insert on test_triggers for each statement execute procedure say_something('statement trigger');
+create trigger say_hello_ra after update on test_triggers for each row execute procedure say_something('after row trigger');
+create trigger say_hello_ra2 after update on test_triggers for each row execute procedure say_something2('another after row trigger');
+insert into test_triggers values (1, 'foo');
+NOTICE:  statement trigger
+update test_triggers set b = 'bar' where a = 1;
+NOTICE:  after row trigger
+NOTICE:  another after row trigger
+create trigger say_hello_rb before update on test_triggers for each row execute procedure say_something('before row trigger');  -- will fail
+update test_triggers set b = 'baz' where a = 1;
+NOTICE:  before row trigger
+ERROR:  control reached end of trigger procedure without RETURN
+DETAIL:  A trigger procedure used in a row-level trigger that is not fired AFTER must return a value.
+CONTEXT:  PL/pgSQL function "say_something"
+drop trigger say_hello_rb on test_triggers;
+-- XXX plain RETURN behaves like RETURN NULL
+create trigger say_hello_rb2 before update on test_triggers for each row execute procedure say_something2('another before row trigger');
+update test_triggers set b = 'baz' where a = 1;
+NOTICE:  another before row trigger
+select * from test_triggers order by a, b;
+ a |  b  
+---+-----
+ 1 | bar
+(1 row)
+
+drop trigger say_hello_rb2 on test_triggers;
+drop table test_triggers;
+drop function say_something();
+drop function say_something2();
diff --git i/src/test/regress/sql/plpgsql.sql w/src/test/regress/sql/plpgsql.sql
index b47c2de..167b1fe 100644
--- i/src/test/regress/sql/plpgsql.sql
+++ w/src/test/regress/sql/plpgsql.sql
@@ -3600,3 +3600,44 @@ select testoa(1,2,1); -- fail at update
 
 drop function arrayassign1();
 drop function testoa(x1 int, x2 int, x3 int);
+
+--
+-- Additional triggers tests
+--
+
+create table test_triggers (a int, b text);
+
+-- trigger function without return statement
+create function say_something() returns trigger
+language plpgsql as $$
+begin
+    raise notice '%', tg_argv[0];
+end$$;
+
+-- trigger function with RETURN without argument
+create function say_something2() returns trigger
+language plpgsql as $$
+begin
+    raise notice '%', tg_argv[0];
+    return;
+end$$;
+
+create trigger say_hello_s before insert on test_triggers for each statement execute procedure say_something('statement trigger');
+create trigger say_hello_ra after update on test_triggers for each row execute procedure say_something('after row trigger');
+create trigger say_hello_ra2 after update on test_triggers for each row execute procedure say_something2('another after row trigger');
+insert into test_triggers values (1, 'foo');
+update test_triggers set b = 'bar' where a = 1;
+
+create trigger say_hello_rb before update on test_triggers for each row execute procedure say_something('before row trigger');  -- will fail
+update test_triggers set b = 'baz' where a = 1;
+drop trigger say_hello_rb on test_triggers;
+
+-- XXX plain RETURN behaves like RETURN NULL
+create trigger say_hello_rb2 before update on test_triggers for each row execute procedure say_something2('another before row trigger');
+update test_triggers set b = 'baz' where a = 1;
+select * from test_triggers order by a, b;
+drop trigger say_hello_rb2 on test_triggers;
+
+drop table test_triggers;
+drop function say_something();
+drop function say_something2();