diff --git a/src/backend/utils/adt/int8.c b/src/backend/utils/adt/int8.c
index 98d4323755..464b64bb5e 100644
--- a/src/backend/utils/adt/int8.c
+++ b/src/backend/utils/adt/int8.c
@@ -833,6 +833,21 @@ int8inc_support(PG_FUNCTION_ARGS)
 		SupportRequestWFuncMonotonic *req = (SupportRequestWFuncMonotonic *) rawreq;
 		MonotonicFunction monotonic = MONOTONICFUNC_NONE;
 		int			frameOptions = req->window_clause->frameOptions;
+		WindowFunc *wfunc = req->window_func;
+
+		if (list_length(wfunc->args) == 1)
+		{
+			Node *expr = eval_const_expressions(NULL, linitial(wfunc->args));
+
+			/*
+			 * Due to the Node representation of WindowClause runConditions in
+			 * version prior to v17, we need to insist that the count arg is
+			 * Const to allow safe application of the runCondition
+			 * optimization.
+			 */
+			if (!IsA(expr, Const))
+				PG_RETURN_POINTER(NULL);
+		}
 
 		/* No ORDER BY clause then all rows are peers */
 		if (req->window_clause->orderClause == NIL)
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index 596564fa15..871119eeec 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -14,6 +14,7 @@
 #include "postgres.h"
 
 #include "nodes/supportnodes.h"
+#include "optimizer/optimizer.h"
 #include "utils/builtins.h"
 #include "windowapi.h"
 
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 1f23baa3cc..f8914c0401 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -3481,13 +3481,13 @@ EXPLAIN (COSTS OFF)
 SELECT * FROM
   (SELECT empno,
           salary,
-          count(empno) OVER (ORDER BY salary DESC) c
+          count(1) OVER (ORDER BY salary DESC) c
    FROM empsalary) emp
 WHERE c <= 3;
-                       QUERY PLAN                        
----------------------------------------------------------
+                QUERY PLAN                 
+-------------------------------------------
  WindowAgg
-   Run Condition: (count(empsalary.empno) OVER (?) <= 3)
+   Run Condition: (count(1) OVER (?) <= 3)
    ->  Sort
          Sort Key: empsalary.salary DESC
          ->  Seq Scan on empsalary
@@ -3496,7 +3496,7 @@ WHERE c <= 3;
 SELECT * FROM
   (SELECT empno,
           salary,
-          count(empno) OVER (ORDER BY salary DESC) c
+          count(1) OVER (ORDER BY salary DESC) c
    FROM empsalary) emp
 WHERE c <= 3;
  empno | salary | c 
@@ -3608,19 +3608,19 @@ WHERE rn < 3;
                ->  Seq Scan on empsalary
 (6 rows)
 
--- likewise with count(empno) instead of row_number()
+-- likewise with count(1) instead of row_number()
 EXPLAIN (COSTS OFF)
 SELECT * FROM
   (SELECT empno,
           depname,
           salary,
-          count(empno) OVER (PARTITION BY depname ORDER BY salary DESC) c
+          count(1) OVER (PARTITION BY depname ORDER BY salary DESC) c
    FROM empsalary) emp
 WHERE c <= 3;
                          QUERY PLAN                         
 ------------------------------------------------------------
  WindowAgg
-   Run Condition: (count(empsalary.empno) OVER (?) <= 3)
+   Run Condition: (count(1) OVER (?) <= 3)
    ->  Sort
          Sort Key: empsalary.depname, empsalary.salary DESC
          ->  Seq Scan on empsalary
@@ -3631,7 +3631,7 @@ SELECT * FROM
   (SELECT empno,
           depname,
           salary,
-          count(empno) OVER (PARTITION BY depname ORDER BY salary DESC) c
+          count(1) OVER (PARTITION BY depname ORDER BY salary DESC) c
    FROM empsalary) emp
 WHERE c <= 3;
  empno |  depname  | salary | c 
@@ -3653,13 +3653,13 @@ SELECT * FROM
   (SELECT empno,
           depname,
           salary,
-          count(empno) OVER () c
+          count(1) OVER () c
    FROM empsalary) emp
 WHERE c = 1;
-                       QUERY PLAN                       
---------------------------------------------------------
+                QUERY PLAN                
+------------------------------------------
  WindowAgg
-   Run Condition: (count(empsalary.empno) OVER (?) = 1)
+   Run Condition: (count(1) OVER (?) = 1)
    ->  Seq Scan on empsalary
 (3 rows)
 
@@ -3667,7 +3667,7 @@ WHERE c = 1;
 EXPLAIN (COSTS OFF)
 SELECT * FROM
   (SELECT *,
-          count(salary) OVER (PARTITION BY depname || '') c1, -- w1
+          count(1) OVER (PARTITION BY depname || '') c1, -- w1
           row_number() OVER (PARTITION BY depname) rn, -- w2
           count(*) OVER (PARTITION BY depname) c2, -- w2
           count(*) OVER (PARTITION BY '' || depname) c3 -- w3
@@ -3678,7 +3678,7 @@ SELECT * FROM
  Subquery Scan on e
    ->  WindowAgg
          Filter: ((row_number() OVER (?)) <= 1)
-         Run Condition: (count(empsalary.salary) OVER (?) <= 3)
+         Run Condition: (count(1) OVER (?) <= 3)
          ->  Sort
                Sort Key: (((empsalary.depname)::text || ''::text))
                ->  WindowAgg
@@ -3694,7 +3694,7 @@ SELECT * FROM
 -- Ensure we correctly filter out all of the run conditions from each window
 SELECT * FROM
   (SELECT *,
-          count(salary) OVER (PARTITION BY depname || '') c1, -- w1
+          count(1) OVER (PARTITION BY depname || '') c1, -- w1
           row_number() OVER (PARTITION BY depname) rn, -- w2
           count(*) OVER (PARTITION BY depname) c2, -- w2
           count(*) OVER (PARTITION BY '' || depname) c3 -- w3
@@ -3765,6 +3765,24 @@ WHERE c = 1;
                ->  Seq Scan on empsalary
 (6 rows)
 
+-- Ensure we don't use a run condition when the WindowFunc arg contains a Var
+EXPLAIN (COSTS OFF)
+SELECT * FROM
+  (SELECT empno,
+          salary,
+          count(empno) OVER (ORDER BY empno DESC) c
+   FROM empsalary) emp
+WHERE c = 1;
+                  QUERY PLAN                  
+----------------------------------------------
+ Subquery Scan on emp
+   Filter: (emp.c = 1)
+   ->  WindowAgg
+         ->  Sort
+               Sort Key: empsalary.empno DESC
+               ->  Seq Scan on empsalary
+(6 rows)
+
 -- Ensure we don't use a run condition when the WindowFunc contains subplans
 EXPLAIN (COSTS OFF)
 SELECT * FROM
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 253c1b7089..2a5aa38d29 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1068,14 +1068,14 @@ EXPLAIN (COSTS OFF)
 SELECT * FROM
   (SELECT empno,
           salary,
-          count(empno) OVER (ORDER BY salary DESC) c
+          count(1) OVER (ORDER BY salary DESC) c
    FROM empsalary) emp
 WHERE c <= 3;
 
 SELECT * FROM
   (SELECT empno,
           salary,
-          count(empno) OVER (ORDER BY salary DESC) c
+          count(1) OVER (ORDER BY salary DESC) c
    FROM empsalary) emp
 WHERE c <= 3;
 
@@ -1131,13 +1131,13 @@ SELECT empno, depname FROM
    FROM empsalary) emp
 WHERE rn < 3;
 
--- likewise with count(empno) instead of row_number()
+-- likewise with count(1) instead of row_number()
 EXPLAIN (COSTS OFF)
 SELECT * FROM
   (SELECT empno,
           depname,
           salary,
-          count(empno) OVER (PARTITION BY depname ORDER BY salary DESC) c
+          count(1) OVER (PARTITION BY depname ORDER BY salary DESC) c
    FROM empsalary) emp
 WHERE c <= 3;
 
@@ -1146,7 +1146,7 @@ SELECT * FROM
   (SELECT empno,
           depname,
           salary,
-          count(empno) OVER (PARTITION BY depname ORDER BY salary DESC) c
+          count(1) OVER (PARTITION BY depname ORDER BY salary DESC) c
    FROM empsalary) emp
 WHERE c <= 3;
 
@@ -1157,7 +1157,7 @@ SELECT * FROM
   (SELECT empno,
           depname,
           salary,
-          count(empno) OVER () c
+          count(1) OVER () c
    FROM empsalary) emp
 WHERE c = 1;
 
@@ -1165,7 +1165,7 @@ WHERE c = 1;
 EXPLAIN (COSTS OFF)
 SELECT * FROM
   (SELECT *,
-          count(salary) OVER (PARTITION BY depname || '') c1, -- w1
+          count(1) OVER (PARTITION BY depname || '') c1, -- w1
           row_number() OVER (PARTITION BY depname) rn, -- w2
           count(*) OVER (PARTITION BY depname) c2, -- w2
           count(*) OVER (PARTITION BY '' || depname) c3 -- w3
@@ -1175,7 +1175,7 @@ SELECT * FROM
 -- Ensure we correctly filter out all of the run conditions from each window
 SELECT * FROM
   (SELECT *,
-          count(salary) OVER (PARTITION BY depname || '') c1, -- w1
+          count(1) OVER (PARTITION BY depname || '') c1, -- w1
           row_number() OVER (PARTITION BY depname) rn, -- w2
           count(*) OVER (PARTITION BY depname) c2, -- w2
           count(*) OVER (PARTITION BY '' || depname) c3 -- w3
@@ -1215,6 +1215,15 @@ SELECT * FROM
    FROM empsalary) emp
 WHERE c = 1;
 
+-- Ensure we don't use a run condition when the WindowFunc arg contains a Var
+EXPLAIN (COSTS OFF)
+SELECT * FROM
+  (SELECT empno,
+          salary,
+          count(empno) OVER (ORDER BY empno DESC) c
+   FROM empsalary) emp
+WHERE c = 1;
+
 -- Ensure we don't use a run condition when the WindowFunc contains subplans
 EXPLAIN (COSTS OFF)
 SELECT * FROM