diff --git a/libdm/ioctl/libdevmapper.c b/libdm/ioctl/libdevmapper.c
index e8f165ed7..ad005548b 100644
--- a/libdm/ioctl/libdevmapper.c
+++ b/libdm/ioctl/libdevmapper.c
@@ -157,6 +157,8 @@ static struct dm_ioctl *_flatten(struct dm_task *dmt)
 	if (!(dmi = malloc(len)))
 		return NULL;
 
+	memset(dmi, 0, len);
+
 	strncpy(dmi->version, DM_IOCTL_VERSION, sizeof(dmi->version));
 	dmi->data_size = len;
 	strncpy(dmi->name, dmt->dev_name, sizeof(dmi->name));