diff --git a/libfprint/async.c b/libfprint/async.c
index f469a36f..35da8758 100644
--- a/libfprint/async.c
+++ b/libfprint/async.c
@@ -47,11 +47,15 @@ void fpi_drvcb_open_complete(struct fp_dev *dev, int status)
 API_EXPORTED int fp_async_dev_open(struct fp_dscv_dev *ddev, fp_dev_open_cb callback,
 	void *user_data)
 {
-	struct fp_driver *drv = ddev->drv;
+	struct fp_driver *drv;
 	struct fp_dev *dev;
 	libusb_device_handle *udevh;
 	int r;
 
+	g_return_val_if_fail(ddev != NULL, -ENODEV);
+
+	drv = ddev->drv;
+
 	G_DEBUG_HERE();
 	r = libusb_open(ddev->udev, &udevh);
 	if (r < 0) {
@@ -104,7 +108,11 @@ void fpi_drvcb_close_complete(struct fp_dev *dev)
 API_EXPORTED void fp_async_dev_close(struct fp_dev *dev,
 	fp_operation_stop_cb callback, void *user_data)
 {
-	struct fp_driver *drv = dev->drv;
+	struct fp_driver *drv;
+
+	g_return_if_fail (dev != NULL);
+
+	drv = dev->drv;
 
 	if (g_slist_index(opened_devices, (gconstpointer) dev) == -1)
 		fp_err("device %p not in opened list!", dev);
@@ -152,9 +160,13 @@ void fpi_drvcb_enroll_started(struct fp_dev *dev, int status)
 API_EXPORTED int fp_async_enroll_start(struct fp_dev *dev,
 	fp_enroll_stage_cb callback, void *user_data)
 {
-	struct fp_driver *drv = dev->drv;
+	struct fp_driver *drv;
 	int r;
 
+	g_return_val_if_fail(dev != NULL, -ENODEV);
+
+	drv = dev->drv;
+
 	if (!dev->nr_enroll_stages || !drv->enroll_start) {
 		fp_err("driver %s has 0 enroll stages or no enroll func",
 			drv->name);
@@ -214,9 +226,13 @@ void fpi_drvcb_enroll_stopped(struct fp_dev *dev)
 API_EXPORTED int fp_async_enroll_stop(struct fp_dev *dev,
 	fp_operation_stop_cb callback, void *user_data)
 {
-	struct fp_driver *drv = dev->drv;
+	struct fp_driver *drv;
 	int r;
 
+	g_return_val_if_fail(dev != NULL, -ENODEV);
+
+	drv = dev->drv;
+
 	G_DEBUG_HERE();
 	if (!drv->enroll_start)
 		return -ENOTSUP;
@@ -252,9 +268,13 @@ API_EXPORTED int fp_async_enroll_stop(struct fp_dev *dev,
 API_EXPORTED int fp_async_verify_start(struct fp_dev *dev,
 	struct fp_print_data *data, fp_img_operation_cb callback, void *user_data)
 {
-	struct fp_driver *drv = dev->drv;
+	struct fp_driver *drv;
 	int r;
 
+	g_return_val_if_fail(dev != NULL, -ENODEV);
+
+	drv = dev->drv;
+
 	G_DEBUG_HERE();
 	if (!drv->verify_start)
 		return -ENOTSUP;
@@ -328,10 +348,14 @@ void fpi_drvcb_verify_stopped(struct fp_dev *dev)
 API_EXPORTED int fp_async_verify_stop(struct fp_dev *dev,
 	fp_operation_stop_cb callback, void *user_data)
 {
-	struct fp_driver *drv = dev->drv;
+	struct fp_driver *drv;
 	gboolean iterating = (dev->state == DEV_STATE_VERIFYING);
 	int r;
 
+	g_return_val_if_fail(dev != NULL, -ENODEV);
+
+	drv = dev->drv;
+
 	G_DEBUG_HERE();
 	BUG_ON(dev->state != DEV_STATE_ERROR
 		&& dev->state != DEV_STATE_VERIFYING
@@ -370,9 +394,13 @@ API_EXPORTED int fp_async_verify_stop(struct fp_dev *dev,
 API_EXPORTED int fp_async_identify_start(struct fp_dev *dev,
 	struct fp_print_data **gallery, fp_identify_cb callback, void *user_data)
 {
-	struct fp_driver *drv = dev->drv;
+	struct fp_driver *drv;
 	int r;
 
+	g_return_val_if_fail(dev != NULL, -ENODEV);
+
+	drv = dev->drv;
+
 	G_DEBUG_HERE();
 	if (!drv->identify_start)
 		return -ENOTSUP;
@@ -436,10 +464,14 @@ void fpi_drvcb_report_identify_result(struct fp_dev *dev, int result,
 API_EXPORTED int fp_async_identify_stop(struct fp_dev *dev,
 	fp_operation_stop_cb callback, void *user_data)
 {
-	struct fp_driver *drv = dev->drv;
+	struct fp_driver *drv;
 	gboolean iterating = (dev->state == DEV_STATE_IDENTIFYING);
 	int r;
 
+	g_return_val_if_fail(dev != NULL, -ENODEV);
+
+	drv = dev->drv;
+
 	G_DEBUG_HERE();
 	BUG_ON(dev->state != DEV_STATE_IDENTIFYING
 		&& dev->state != DEV_STATE_IDENTIFY_DONE);
@@ -488,9 +520,13 @@ void fpi_drvcb_identify_stopped(struct fp_dev *dev)
 API_EXPORTED int fp_async_capture_start(struct fp_dev *dev, int unconditional,
 	fp_img_operation_cb callback, void *user_data)
 {
-	struct fp_driver *drv = dev->drv;
+	struct fp_driver *drv;
 	int r;
 
+	g_return_val_if_fail(dev != NULL, -ENODEV);
+
+	drv = dev->drv;
+
 	G_DEBUG_HERE();
 	if (!drv->capture_start)
 		return -ENOTSUP;
@@ -563,9 +599,13 @@ void fpi_drvcb_capture_stopped(struct fp_dev *dev)
 API_EXPORTED int fp_async_capture_stop(struct fp_dev *dev,
 	fp_operation_stop_cb callback, void *user_data)
 {
-	struct fp_driver *drv = dev->drv;
+	struct fp_driver *drv;
 	int r;
 
+	g_return_val_if_fail(dev != NULL, -ENODEV);
+
+	drv = dev->drv;
+
 	G_DEBUG_HERE();
 	BUG_ON(dev->state != DEV_STATE_ERROR
 		&& dev->state != DEV_STATE_CAPTURING