diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 81ba024bba..4f4aeb2883 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2300,7 +2300,27 @@ ExecWindowAgg(PlanState *pstate)
 						continue;
 					}
 					else
+					{
 						winstate->status = WINDOWAGG_PASSTHROUGH;
+
+						/*
+						 * If we're not the top-window, we'd better NULLify
+						 * the aggregate results.  In pass-through mode we no
+						 * longer update these and this avoids the old stale
+						 * results lingering.  Some of these might be byref
+						 * types so we can't have them pointing to free'd
+						 * memory.  The planner insisted that quals used in
+						 * the runcondition are strict, so the top-level
+						 * WindowAgg will filter these NULLs out in the filter
+						 * clause.
+						 */
+						numfuncs = winstate->numfuncs;
+						for (i = 0; i < numfuncs; i++)
+						{
+							econtext->ecxt_aggvalues[i] = (Datum) 0;
+							econtext->ecxt_aggnulls[i] = true;
+						}
+					}
 				}
 				else
 				{
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 03ee6dc832..0c564be7f6 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -2399,6 +2399,18 @@ check_and_push_window_quals(Query *subquery, RangeTblEntry *rte, Index rti,
 	if (list_length(opexpr->args) != 2)
 		return true;
 
+	/*
+	 * Currently, we restrict this optimization to strict OpExprs.  The reason
+	 * for this is that during execution, once the runcondition becomes false,
+	 * we stop evaluating WindowFuncs.  To avoid leaving around stale window
+	 * function result values, we set them to NULL.  Having only strict
+	 * OpExprs here ensures that we properly filter out the tuples with NULLs
+	 * in the top-level WindowAgg.
+	 */
+	set_opfuncid(opexpr);
+	if (!func_strict(opexpr->opfuncid))
+		return true;
+
 	/*
 	 * Check for plain Vars that reference window functions in the subquery.
 	 * If we find any, we'll ask find_window_run_conditions() if 'opexpr' can