diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c
index fb768ad52c..41da670f15 100644
--- a/src/backend/optimizer/prep/prepjointree.c
+++ b/src/backend/optimizer/prep/prepjointree.c
@@ -153,7 +153,7 @@ transform_MERGE_to_join(Query *parse)
 {
 	RangeTblEntry *joinrte;
 	JoinExpr   *joinexpr;
-	bool		have_action[3];
+	bool		have_action[NUM_MERGE_MATCH_KINDS];
 	JoinType	jointype;
 	int			joinrti;
 	List	   *vars;
diff --git a/src/backend/parser/parse_merge.c b/src/backend/parser/parse_merge.c
index bce11d5956..87df79027d 100644
--- a/src/backend/parser/parse_merge.c
+++ b/src/backend/parser/parse_merge.c
@@ -109,7 +109,7 @@ transformMergeStmt(ParseState *pstate, MergeStmt *stmt)
 	Query	   *qry = makeNode(Query);
 	ListCell   *l;
 	AclMode		targetPerms = ACL_NO_RIGHTS;
-	bool		is_terminal[3];
+	bool		is_terminal[NUM_MERGE_MATCH_KINDS];
 	Index		sourceRTI;
 	List	   *mergeActionList;
 	ParseNamespaceItem *nsitem;
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index fa2f70b7a4..c1a65bad2a 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -545,7 +545,7 @@ typedef struct ResultRelInfo
 	OnConflictSetState *ri_onConflict;
 
 	/* for MERGE, lists of MergeActionState (one per MergeMatchKind) */
-	List	   *ri_MergeActions[3];
+	List	   *ri_MergeActions[NUM_MERGE_MATCH_KINDS];
 
 	/* for MERGE, expr state for checking the join condition */
 	ExprState  *ri_MergeJoinCondition;
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 719c4b7b61..247cecb4b4 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -1970,6 +1970,8 @@ typedef enum MergeMatchKind
 	MERGE_WHEN_NOT_MATCHED_BY_TARGET
 } MergeMatchKind;
 
+#define NUM_MERGE_MATCH_KINDS (MERGE_WHEN_NOT_MATCHED_BY_TARGET + 1)
+
 typedef struct MergeAction
 {
 	NodeTag		type;