diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index 893b76703da6..6f5be9e5ede4 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -314,6 +314,11 @@ static int cros_ec_get_proto_info(struct cros_ec_device *ec_dev, int devidx)
 		goto exit;
 	}
 
+	if (ret == 0) {
+		ret = -EPROTO;
+		goto exit;
+	}
+
 	info = (struct ec_response_get_protocol_info *)msg->data;
 
 	switch (devidx) {
diff --git a/drivers/platform/chrome/cros_ec_proto_test.c b/drivers/platform/chrome/cros_ec_proto_test.c
index 14a4441a39fc..473714964cf2 100644
--- a/drivers/platform/chrome/cros_ec_proto_test.c
+++ b/drivers/platform/chrome/cros_ec_proto_test.c
@@ -406,6 +406,71 @@ static void cros_ec_proto_test_query_all_no_pd_return_error(struct kunit *test)
 	}
 }
 
+static void cros_ec_proto_test_query_all_no_pd_return0(struct kunit *test)
+{
+	struct cros_ec_proto_test_priv *priv = test->priv;
+	struct cros_ec_device *ec_dev = &priv->ec_dev;
+	struct ec_xfer_mock *mock;
+	int ret;
+
+	/* Set some garbage bytes. */
+	ec_dev->max_passthru = 0xbf;
+
+	/* For cros_ec_get_proto_info() without passthru. */
+	{
+		struct ec_response_get_protocol_info *data;
+
+		mock = cros_kunit_ec_xfer_mock_add(test, sizeof(*data));
+		KUNIT_ASSERT_PTR_NE(test, mock, NULL);
+
+		/*
+		 * Although it doesn't check the value, provides valid sizes so that
+		 * cros_ec_query_all() allocates din and dout correctly.
+		 */
+		data = (struct ec_response_get_protocol_info *)mock->o_data;
+		data->max_request_packet_size = 0xbe;
+		data->max_response_packet_size = 0xef;
+	}
+
+	/* For cros_ec_get_proto_info() with passthru. */
+	{
+		mock = cros_kunit_ec_xfer_mock_add(test, 0);
+		KUNIT_ASSERT_PTR_NE(test, mock, NULL);
+	}
+
+	cros_ec_proto_test_query_all_pretest(test);
+	ret = cros_ec_query_all(ec_dev);
+	KUNIT_EXPECT_EQ(test, ret, 0);
+
+	/* For cros_ec_get_proto_info() without passthru. */
+	{
+		mock = cros_kunit_ec_xfer_mock_next();
+		KUNIT_EXPECT_PTR_NE(test, mock, NULL);
+
+		KUNIT_EXPECT_EQ(test, mock->msg.version, 0);
+		KUNIT_EXPECT_EQ(test, mock->msg.command, EC_CMD_GET_PROTOCOL_INFO);
+		KUNIT_EXPECT_EQ(test, mock->msg.insize,
+				sizeof(struct ec_response_get_protocol_info));
+		KUNIT_EXPECT_EQ(test, mock->msg.outsize, 0);
+	}
+
+	/* For cros_ec_get_proto_info() with passthru. */
+	{
+		mock = cros_kunit_ec_xfer_mock_next();
+		KUNIT_EXPECT_PTR_NE(test, mock, NULL);
+
+		KUNIT_EXPECT_EQ(test, mock->msg.version, 0);
+		KUNIT_EXPECT_EQ(test, mock->msg.command,
+				EC_CMD_PASSTHRU_OFFSET(CROS_EC_DEV_PD_INDEX) |
+				EC_CMD_GET_PROTOCOL_INFO);
+		KUNIT_EXPECT_EQ(test, mock->msg.insize,
+				sizeof(struct ec_response_get_protocol_info));
+		KUNIT_EXPECT_EQ(test, mock->msg.outsize, 0);
+
+		KUNIT_EXPECT_EQ(test, ec_dev->max_passthru, 0);
+	}
+}
+
 static void cros_ec_proto_test_query_all_legacy_normal_v3_return_error(struct kunit *test)
 {
 	struct cros_ec_proto_test_priv *priv = test->priv;
@@ -471,6 +536,71 @@ static void cros_ec_proto_test_query_all_legacy_normal_v3_return_error(struct ku
 	}
 }
 
+static void cros_ec_proto_test_query_all_legacy_normal_v3_return0(struct kunit *test)
+{
+	struct cros_ec_proto_test_priv *priv = test->priv;
+	struct cros_ec_device *ec_dev = &priv->ec_dev;
+	struct ec_xfer_mock *mock;
+	int ret;
+
+	/* For cros_ec_get_proto_info() without passthru. */
+	{
+		mock = cros_kunit_ec_xfer_mock_add(test, 0);
+		KUNIT_ASSERT_PTR_NE(test, mock, NULL);
+	}
+
+	/* For cros_ec_host_command_proto_query_v2(). */
+	{
+		struct ec_response_hello *data;
+
+		mock = cros_kunit_ec_xfer_mock_add(test, sizeof(*data));
+		KUNIT_ASSERT_PTR_NE(test, mock, NULL);
+
+		data = (struct ec_response_hello *)mock->o_data;
+		data->out_data = 0xa1b2c3d4;
+	}
+
+	cros_ec_proto_test_query_all_pretest(test);
+	ret = cros_ec_query_all(ec_dev);
+	KUNIT_EXPECT_EQ(test, ret, 0);
+
+	/* For cros_ec_get_proto_info() without passthru. */
+	{
+		mock = cros_kunit_ec_xfer_mock_next();
+		KUNIT_EXPECT_PTR_NE(test, mock, NULL);
+
+		KUNIT_EXPECT_EQ(test, mock->msg.version, 0);
+		KUNIT_EXPECT_EQ(test, mock->msg.command, EC_CMD_GET_PROTOCOL_INFO);
+		KUNIT_EXPECT_EQ(test, mock->msg.insize,
+				sizeof(struct ec_response_get_protocol_info));
+		KUNIT_EXPECT_EQ(test, mock->msg.outsize, 0);
+	}
+
+	/* For cros_ec_host_command_proto_query_v2(). */
+	{
+		struct ec_params_hello *data;
+
+		mock = cros_kunit_ec_xfer_mock_next();
+		KUNIT_EXPECT_PTR_NE(test, mock, NULL);
+
+		KUNIT_EXPECT_EQ(test, mock->msg.version, 0);
+		KUNIT_EXPECT_EQ(test, mock->msg.command, EC_CMD_HELLO);
+		KUNIT_EXPECT_EQ(test, mock->msg.insize, sizeof(struct ec_response_hello));
+		KUNIT_EXPECT_EQ(test, mock->msg.outsize, sizeof(*data));
+
+		data = (struct ec_params_hello *)mock->i_data;
+		KUNIT_EXPECT_EQ(test, data->in_data, 0xa0b0c0d0);
+
+		KUNIT_EXPECT_EQ(test, ec_dev->proto_version, 2);
+		KUNIT_EXPECT_EQ(test, ec_dev->max_request, EC_PROTO2_MAX_PARAM_SIZE);
+		KUNIT_EXPECT_EQ(test, ec_dev->max_response, EC_PROTO2_MAX_PARAM_SIZE);
+		KUNIT_EXPECT_EQ(test, ec_dev->max_passthru, 0);
+		KUNIT_EXPECT_PTR_EQ(test, ec_dev->pkt_xfer, NULL);
+		KUNIT_EXPECT_EQ(test, ec_dev->din_size, EC_PROTO2_MSG_BYTES);
+		KUNIT_EXPECT_EQ(test, ec_dev->dout_size, EC_PROTO2_MSG_BYTES);
+	}
+}
+
 static void cros_ec_proto_test_query_all_legacy_xfer_error(struct kunit *test)
 {
 	struct cros_ec_proto_test_priv *priv = test->priv;
@@ -998,7 +1128,9 @@ static struct kunit_case cros_ec_proto_test_cases[] = {
 	KUNIT_CASE(cros_ec_proto_test_check_result),
 	KUNIT_CASE(cros_ec_proto_test_query_all_normal),
 	KUNIT_CASE(cros_ec_proto_test_query_all_no_pd_return_error),
+	KUNIT_CASE(cros_ec_proto_test_query_all_no_pd_return0),
 	KUNIT_CASE(cros_ec_proto_test_query_all_legacy_normal_v3_return_error),
+	KUNIT_CASE(cros_ec_proto_test_query_all_legacy_normal_v3_return0),
 	KUNIT_CASE(cros_ec_proto_test_query_all_legacy_xfer_error),
 	KUNIT_CASE(cros_ec_proto_test_query_all_legacy_return_error),
 	KUNIT_CASE(cros_ec_proto_test_query_all_legacy_data_error),
