diff --git a/src/gpt-auto-generator/gpt-auto-generator.c b/src/gpt-auto-generator/gpt-auto-generator.c
index 64ca9bb2f9..28982a4c34 100644
--- a/src/gpt-auto-generator/gpt-auto-generator.c
+++ b/src/gpt-auto-generator/gpt-auto-generator.c
@@ -779,12 +779,16 @@ static int add_mounts(void) {
                         return btrfs_log_dev_root(LOG_ERR, r, "root file system");
                 if (r < 0)
                         return log_error_errno(r, "Failed to determine block device of root file system: %m");
-                if (r == 0) { /* Not backed by block device */
+                if (r == 0) { /* Not backed by a single block device. (Could be NFS or so, or could be multi-device RAID or so) */
                         r = get_block_device_harder("/usr", &devno);
                         if (r == -EUCLEAN)
                                 return btrfs_log_dev_root(LOG_ERR, r, "/usr");
                         if (r < 0)
-                                return log_error_errno(r, "Failed to determine block device of /usr file system: %m");
+                                return log_error_errno(r, "Failed to determine block device of /usr/ file system: %m");
+                        if (r == 0) { /* /usr/ not backed by single block device, either. */
+                                log_debug("Neither root nor /usr/ file system are on a (single) block device.");
+                                return 0;
+                        }
                 }
         } else if (r < 0)
                 return log_error_errno(r, "Failed to read symlink /run/systemd/volatile-root: %m");
diff --git a/src/libsystemd/sd-device/sd-device.c b/src/libsystemd/sd-device/sd-device.c
index 27c91ea724..c9ce3b5c58 100644
--- a/src/libsystemd/sd-device/sd-device.c
+++ b/src/libsystemd/sd-device/sd-device.c
@@ -248,6 +248,10 @@ _public_ int sd_device_new_from_devnum(sd_device **ret, char type, dev_t devnum)
         assert_return(ret, -EINVAL);
         assert_return(IN_SET(type, 'b', 'c'), -EINVAL);
 
+        if (devnum == 0)
+                return log_debug_errno(SYNTHETIC_ERRNO(ENODEV),
+                                       "sd-device: Attempted to allocate device by zero major/minor, refusing.");
+
         /* use /sys/dev/{block,char}/<maj>:<min> link */
         xsprintf(id, "%u:%u", major(devnum), minor(devnum));