diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index cc10c5eb1d..bf40881037 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -165,6 +165,7 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 	HeapTuple	tuple;
 	Oid			funcoid;
 	Oid			funcrettype;
+	Oid			fargtypes[1];	/* dummy */
 	Oid			evtowner = GetUserId();
 	ListCell   *lc;
 	List	   *tags = NULL;
@@ -230,7 +231,7 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 						stmt->trigname)));
 
 	/* Find and validate the trigger function. */
-	funcoid = LookupFuncName(stmt->funcname, 0, NULL, false);
+	funcoid = LookupFuncName(stmt->funcname, 0, fargtypes, false);
 	funcrettype = get_func_rettype(funcoid);
 	if (funcrettype != EVTTRIGGEROID)
 		ereport(ERROR,
diff --git a/src/backend/commands/foreigncmds.c b/src/backend/commands/foreigncmds.c
index 3b85c2c017..cc912b2a79 100644
--- a/src/backend/commands/foreigncmds.c
+++ b/src/backend/commands/foreigncmds.c
@@ -474,12 +474,13 @@ static Oid
 lookup_fdw_handler_func(DefElem *handler)
 {
 	Oid			handlerOid;
+	Oid			funcargtypes[1];	/* dummy */
 
 	if (handler == NULL || handler->arg == NULL)
 		return InvalidOid;
 
 	/* handlers have no arguments */
-	handlerOid = LookupFuncName((List *) handler->arg, 0, NULL, false);
+	handlerOid = LookupFuncName((List *) handler->arg, 0, funcargtypes, false);
 
 	/* check that handler has correct return type */
 	if (get_func_rettype(handlerOid) != FDW_HANDLEROID)
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index fa9761bac3..430baff116 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -1415,6 +1415,9 @@ func_get_detail(List *funcname,
 	FuncCandidateList raw_candidates;
 	FuncCandidateList best_candidate;
 
+	/* Passing NULL for argtypes is no longer allowed */
+	Assert(argtypes);
+
 	/* initialize output arguments to silence compiler warnings */
 	*funcid = InvalidOid;
 	*rettype = InvalidOid;
@@ -2043,6 +2046,9 @@ LookupFuncName(List *funcname, int nargs, const Oid *argtypes, bool noError)
 {
 	FuncCandidateList clist;
 
+	/* Passing NULL for argtypes is no longer allowed */
+	Assert(argtypes);
+
 	clist = FuncnameGetCandidates(funcname, nargs, NIL, false, false, noError);
 
 	while (clist)
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index e316951cf3..2cd4b62701 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -718,6 +718,7 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
 	SysScanDesc tgscan;
 	int			findx = 0;
 	char	   *tgname;
+	Oid			argtypes[1];	/* dummy */
 	Datum		value;
 	bool		isnull;
 
@@ -893,7 +894,7 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
 
 	appendStringInfo(&buf, "EXECUTE PROCEDURE %s(",
 					 generate_function_name(trigrec->tgfoid, 0,
-											NIL, NULL,
+											NIL, argtypes,
 											false, NULL, EXPR_KIND_NONE));
 
 	if (trigrec->tgnargs > 0)