diff --git a/src/backend/executor/execPartition.c b/src/backend/executor/execPartition.c
index b667d03c7f..d4c6833650 100644
--- a/src/backend/executor/execPartition.c
+++ b/src/backend/executor/execPartition.c
@@ -1673,7 +1673,7 @@ ExecInitPruningContext(PartitionPruneContext *context,
 	foreach(lc, pruning_steps)
 	{
 		PartitionPruneStepOp *step = (PartitionPruneStepOp *) lfirst(lc);
-		ListCell   *lc2;
+		ListCell   *lc2 = list_head(step->exprs);
 		int			keyno;
 
 		/* not needed for other step kinds */
@@ -1682,22 +1682,27 @@ ExecInitPruningContext(PartitionPruneContext *context,
 
 		Assert(list_length(step->exprs) <= partnatts);
 
-		keyno = 0;
-		foreach(lc2, step->exprs)
+		for (keyno = 0; keyno < partnatts; keyno++)
 		{
-			Expr	   *expr = (Expr *) lfirst(lc2);
+			if (bms_is_member(keyno, step->nullkeys))
+				continue;
 
-			/* not needed for Consts */
-			if (!IsA(expr, Const))
+			if (lc2 != NULL)
 			{
-				int			stateidx = PruneCxtStateIdx(partnatts,
-														step->step.step_id,
-														keyno);
+				Expr *expr = lfirst(lc2);
 
-				context->exprstates[stateidx] =
-					ExecInitExpr(expr, context->planstate);
+				/* not needed for Consts */
+				if (!IsA(expr, Const))
+				{
+					int			stateidx = PruneCxtStateIdx(partnatts,
+															step->step.step_id,
+															keyno);
+
+					context->exprstates[stateidx] =
+						ExecInitExpr(expr, context->planstate);
+				}
+				lc2 = lnext(lc2);
 			}
-			keyno++;
 		}
 	}
 }