diff --git a/src/backend/utils/adt/orderedsetaggs.c b/src/backend/utils/adt/orderedsetaggs.c
index d98f5a807c..216c498a2f 100644
--- a/src/backend/utils/adt/orderedsetaggs.c
+++ b/src/backend/utils/adt/orderedsetaggs.c
@@ -122,8 +122,8 @@ ordered_set_startup(FunctionCallInfo fcinfo, bool use_tuples)
 		int			numSortCols;
 
 		/*
-		 * Check we're called as aggregate, and get the Agg node's
-		 * group-lifespan context
+		 * Check we're called as aggregate (and not a window function), and
+		 * get the Agg node's group-lifespan context
 		 */
 		if (AggCheckCallContext(fcinfo, &gcontext) != AGG_CONTEXT_AGGREGATE)
 			elog(ERROR, "ordered-set aggregate called in non-aggregate context");
@@ -356,12 +356,7 @@ ordered_set_transition(PG_FUNCTION_ARGS)
 	if (PG_ARGISNULL(0))
 		osastate = ordered_set_startup(fcinfo, false);
 	else
-	{
-		/* safety check */
-		if (AggCheckCallContext(fcinfo, NULL) != AGG_CONTEXT_AGGREGATE)
-			elog(ERROR, "ordered-set aggregate called in non-aggregate context");
 		osastate = (OSAPerGroupState *) PG_GETARG_POINTER(0);
-	}
 
 	/* Load the datum into the tuplesort object, but only if it's not null */
 	if (!PG_ARGISNULL(1))
@@ -389,12 +384,7 @@ ordered_set_transition_multi(PG_FUNCTION_ARGS)
 	if (PG_ARGISNULL(0))
 		osastate = ordered_set_startup(fcinfo, true);
 	else
-	{
-		/* safety check */
-		if (AggCheckCallContext(fcinfo, NULL) != AGG_CONTEXT_AGGREGATE)
-			elog(ERROR, "ordered-set aggregate called in non-aggregate context");
 		osastate = (OSAPerGroupState *) PG_GETARG_POINTER(0);
-	}
 
 	/* Form a tuple from all the other inputs besides the transition value */
 	slot = osastate->qstate->tupslot;
@@ -435,9 +425,7 @@ percentile_disc_final(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int64		rownum;
 
-	/* safety check */
-	if (AggCheckCallContext(fcinfo, NULL) != AGG_CONTEXT_AGGREGATE)
-		elog(ERROR, "ordered-set aggregate called in non-aggregate context");
+	Assert(AggCheckCallContext(fcinfo, NULL) == AGG_CONTEXT_AGGREGATE);
 
 	/* Get and check the percentile argument */
 	if (PG_ARGISNULL(1))
@@ -542,9 +530,7 @@ percentile_cont_final_common(FunctionCallInfo fcinfo,
 	double		proportion;
 	bool		isnull;
 
-	/* safety check */
-	if (AggCheckCallContext(fcinfo, NULL) != AGG_CONTEXT_AGGREGATE)
-		elog(ERROR, "ordered-set aggregate called in non-aggregate context");
+	Assert(AggCheckCallContext(fcinfo, NULL) == AGG_CONTEXT_AGGREGATE);
 
 	/* Get and check the percentile argument */
 	if (PG_ARGISNULL(1))
@@ -752,9 +738,7 @@ percentile_disc_multi_final(PG_FUNCTION_ARGS)
 	bool		isnull = true;
 	int			i;
 
-	/* safety check */
-	if (AggCheckCallContext(fcinfo, NULL) != AGG_CONTEXT_AGGREGATE)
-		elog(ERROR, "ordered-set aggregate called in non-aggregate context");
+	Assert(AggCheckCallContext(fcinfo, NULL) == AGG_CONTEXT_AGGREGATE);
 
 	/* If there were no regular rows, the result is NULL */
 	if (PG_ARGISNULL(0))
@@ -875,9 +859,7 @@ percentile_cont_multi_final_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	int			i;
 
-	/* safety check */
-	if (AggCheckCallContext(fcinfo, NULL) != AGG_CONTEXT_AGGREGATE)
-		elog(ERROR, "ordered-set aggregate called in non-aggregate context");
+	Assert(AggCheckCallContext(fcinfo, NULL) == AGG_CONTEXT_AGGREGATE);
 
 	/* If there were no regular rows, the result is NULL */
 	if (PG_ARGISNULL(0))
@@ -1045,9 +1027,7 @@ mode_final(PG_FUNCTION_ARGS)
 	FmgrInfo   *equalfn;
 	bool		shouldfree;
 
-	/* safety check */
-	if (AggCheckCallContext(fcinfo, NULL) != AGG_CONTEXT_AGGREGATE)
-		elog(ERROR, "ordered-set aggregate called in non-aggregate context");
+	Assert(AggCheckCallContext(fcinfo, NULL) == AGG_CONTEXT_AGGREGATE);
 
 	/* If there were no regular rows, the result is NULL */
 	if (PG_ARGISNULL(0))
@@ -1173,9 +1153,7 @@ hypothetical_rank_common(FunctionCallInfo fcinfo, int flag,
 	TupleTableSlot *slot;
 	int			i;
 
-	/* safety check */
-	if (AggCheckCallContext(fcinfo, NULL) != AGG_CONTEXT_AGGREGATE)
-		elog(ERROR, "ordered-set aggregate called in non-aggregate context");
+	Assert(AggCheckCallContext(fcinfo, NULL) == AGG_CONTEXT_AGGREGATE);
 
 	/* If there were no regular rows, the rank is always 1 */
 	if (PG_ARGISNULL(0))
@@ -1305,9 +1283,7 @@ hypothetical_dense_rank_final(PG_FUNCTION_ARGS)
 	MemoryContext tmpcontext;
 	int			i;
 
-	/* safety check */
-	if (AggCheckCallContext(fcinfo, NULL) != AGG_CONTEXT_AGGREGATE)
-		elog(ERROR, "ordered-set aggregate called in non-aggregate context");
+	Assert(AggCheckCallContext(fcinfo, NULL) == AGG_CONTEXT_AGGREGATE);
 
 	/* If there were no regular rows, the rank is always 1 */
 	if (PG_ARGISNULL(0))