diff --git a/src/backend/commands/copyto.c b/src/backend/commands/copyto.c
index f0e0147c..e6e9c82d 100644
--- a/src/backend/commands/copyto.c
+++ b/src/backend/commands/copyto.c
@@ -1033,7 +1033,7 @@ BeginCopyTo(ParseState *pstate,
 	{
 		cstate->json_buf = makeStringInfo();
 
-		if (attnamelist != NIL && rel)
+		if (rel && list_length(cstate->attnumlist) < tupDesc->natts)
 		{
 			int			natts = list_length(cstate->attnumlist);
 			TupleDesc	resultDesc;
@@ -1041,6 +1041,13 @@ BeginCopyTo(ParseState *pstate,
 			/*
 			 * Build a TupleDesc describing only the selected columns so that
 			 * composite_to_json() emits the right column names and types.
 			 */
 			resultDesc = CreateTemplateTupleDesc(natts);
 
diff --git a/src/test/regress/expected/generated_stored.out b/src/test/regress/expected/generated_stored.out
index 43cddeac..4d329c60 100644
--- a/src/test/regress/expected/generated_stored.out
+++ b/src/test/regress/expected/generated_stored.out
@@ -541,6 +541,12 @@ SELECT * FROM gtest3 ORDER BY a;
  4 | 12
 (4 rows)
 
+-- COPY JSON should exclude generated columns, same as text/CSV
+COPY gtest1 TO stdout WITH (FORMAT json);
+{"a":1}
+{"a":2}
+{"a":3}
+{"a":4}
 -- null values
 CREATE TABLE gtest2 (a int PRIMARY KEY, b int GENERATED ALWAYS AS (NULL) STORED);
 INSERT INTO gtest2 VALUES (1);
diff --git a/src/test/regress/expected/generated_virtual.out b/src/test/regress/expected/generated_virtual.out
index 234061fa..fc41c480 100644
--- a/src/test/regress/expected/generated_virtual.out
+++ b/src/test/regress/expected/generated_virtual.out
@@ -535,6 +535,12 @@ SELECT * FROM gtest3 ORDER BY a;
  4 | 12
 (4 rows)
 
+-- COPY JSON should exclude generated columns, same as text/CSV
+COPY gtest1 TO stdout WITH (FORMAT json);
+{"a":1}
+{"a":2}
+{"a":3}
+{"a":4}
 -- null values
 CREATE TABLE gtest2 (a int PRIMARY KEY, b int GENERATED ALWAYS AS (NULL) VIRTUAL);
 INSERT INTO gtest2 VALUES (1);
diff --git a/src/test/regress/sql/generated_stored.sql b/src/test/regress/sql/generated_stored.sql
index 280021d7..1064839d 100644
--- a/src/test/regress/sql/generated_stored.sql
+++ b/src/test/regress/sql/generated_stored.sql
@@ -239,6 +239,9 @@ COPY gtest3 (a, b) FROM stdin;
 
 SELECT * FROM gtest3 ORDER BY a;
 
+-- COPY JSON should exclude generated columns, same as text/CSV
+COPY gtest1 TO stdout WITH (FORMAT json);
+
 -- null values
 CREATE TABLE gtest2 (a int PRIMARY KEY, b int GENERATED ALWAYS AS (NULL) STORED);
 INSERT INTO gtest2 VALUES (1);
diff --git a/src/test/regress/sql/generated_virtual.sql b/src/test/regress/sql/generated_virtual.sql
index 4d9ad3c5..9b32413e 100644
--- a/src/test/regress/sql/generated_virtual.sql
+++ b/src/test/regress/sql/generated_virtual.sql
@@ -239,6 +239,9 @@ COPY gtest3 (a, b) FROM stdin;
 
 SELECT * FROM gtest3 ORDER BY a;
 
+-- COPY JSON should exclude generated columns, same as text/CSV
+COPY gtest1 TO stdout WITH (FORMAT json);
+
 -- null values
 CREATE TABLE gtest2 (a int PRIMARY KEY, b int GENERATED ALWAYS AS (NULL) VIRTUAL);
 INSERT INTO gtest2 VALUES (1);