diff --git a/src/backend/parser/parse_merge.c b/src/backend/parser/parse_merge.c
new file mode 100644
index 3844f2b..47d266b
--- a/src/backend/parser/parse_merge.c
+++ b/src/backend/parser/parse_merge.c
@@ -155,12 +155,12 @@ transformMergeStmt(ParseState *pstate, M
 		/*
 		 * Check for unreachable WHEN clauses
 		 */
-		if (mergeWhenClause->condition == NULL)
-			is_terminal[when_type] = true;
-		else if (is_terminal[when_type])
+		if (is_terminal[when_type])
 			ereport(ERROR,
 					(errcode(ERRCODE_SYNTAX_ERROR),
 					 errmsg("unreachable WHEN clause specified after unconditional WHEN clause")));
+		if (mergeWhenClause->condition == NULL)
+			is_terminal[when_type] = true;
 	}
 
 	/*
diff --git a/src/test/regress/expected/merge.out b/src/test/regress/expected/merge.out
new file mode 100644
index 6c8a18f..bc53b21
--- a/src/test/regress/expected/merge.out
+++ b/src/test/regress/expected/merge.out
@@ -659,7 +659,7 @@ USING source AS s
 ON t.tid = s.sid
 WHEN MATCHED THEN /* Terminal WHEN clause for MATCHED */
 	DELETE
-WHEN MATCHED AND s.delta > 0 THEN
+WHEN MATCHED THEN
 	UPDATE SET balance = t.balance - s.delta;
 ERROR:  unreachable WHEN clause specified after unconditional WHEN clause
 ROLLBACK;
diff --git a/src/test/regress/sql/merge.sql b/src/test/regress/sql/merge.sql
new file mode 100644
index 98fe104..fdbcd70
--- a/src/test/regress/sql/merge.sql
+++ b/src/test/regress/sql/merge.sql
@@ -438,7 +438,7 @@ USING source AS s
 ON t.tid = s.sid
 WHEN MATCHED THEN /* Terminal WHEN clause for MATCHED */
 	DELETE
-WHEN MATCHED AND s.delta > 0 THEN
+WHEN MATCHED THEN
 	UPDATE SET balance = t.balance - s.delta;
 ROLLBACK;