diff --git a/core/src/test/resources/sql/sub-query.iq b/core/src/test/resources/sql/sub-query.iq
index aa43c54d923f..0d1b165705c0 100644
--- a/core/src/test/resources/sql/sub-query.iq
+++ b/core/src/test/resources/sql/sub-query.iq
@@ -3686,6 +3686,7 @@ FROM dept d1;
 !ok
 
 # [CALCITE-6041] MAP sub-query gives NullPointerException
+# map size > 1
 SELECT map(SELECT empno, deptno from emp where deptno < 20);
 +-----------------------------+
 | EXPR$0                      |
@@ -3696,4 +3697,28 @@ SELECT map(SELECT empno, deptno from emp where deptno < 20);
 
 !ok
 
+# [CALCITE-6041] MAP sub-query gives NullPointerException
+# map size = 1
+SELECT map(SELECT empno, deptno from emp where empno = 7369);
++-----------+
+| EXPR$0    |
++-----------+
+| {7369=20} |
++-----------+
+(1 row)
+
+!ok
+
+# [CALCITE-6041] MAP sub-query gives NullPointerException
+# empty map
+SELECT map(SELECT empno, deptno from emp where false);
++--------+
+| EXPR$0 |
++--------+
+| {}     |
++--------+
+(1 row)
+
+!ok
+
 # End sub-query.iq