diff --git a/src/libsystemd/sd-id128/id128-util.c b/src/libsystemd/sd-id128/id128-util.c
index 335f22b920..ebbfb2d32e 100644
--- a/src/libsystemd/sd-id128/id128-util.c
+++ b/src/libsystemd/sd-id128/id128-util.c
@@ -10,6 +10,7 @@
 #include "id128-util.h"
 #include "io-util.h"
 #include "stdio-util.h"
+#include "string-util.h"
 
 char *id128_to_uuid_string(sd_id128_t id, char s[static ID128_UUID_STRING_MAX]) {
         unsigned n, k = 0;
@@ -97,6 +98,11 @@ int id128_read_fd(int fd, Id128Format f, sd_id128_t *ret) {
 
         switch (l) {
 
+        case 13:
+        case 14:
+                /* Treat an "uninitialized" id file like an empty one */
+                return f == ID128_PLAIN_OR_UNINIT && strneq(buffer, "uninitialized\n", l) ? -ENOMEDIUM : -EINVAL;
+
         case 33: /* plain UUID with trailing newline */
                 if (buffer[32] != '\n')
                         return -EINVAL;
@@ -115,7 +121,7 @@ int id128_read_fd(int fd, Id128Format f, sd_id128_t *ret) {
 
                 _fallthrough_;
         case 36: /* RFC UUID without trailing newline */
-                if (f == ID128_PLAIN)
+                if (IN_SET(f, ID128_PLAIN, ID128_PLAIN_OR_UNINIT))
                         return -EINVAL;
 
                 buffer[36] = 0;
diff --git a/src/libsystemd/sd-id128/id128-util.h b/src/libsystemd/sd-id128/id128-util.h
index 1901bf119f..1453c00f2f 100644
--- a/src/libsystemd/sd-id128/id128-util.h
+++ b/src/libsystemd/sd-id128/id128-util.h
@@ -17,6 +17,10 @@ bool id128_is_valid(const char *s) _pure_;
 typedef enum Id128Format {
         ID128_ANY,
         ID128_PLAIN,  /* formatted as 32 hex chars as-is */
+        ID128_PLAIN_OR_UNINIT,  /* formatted as 32 hex chars as-is; allow special "uninitialized"
+                                 * value when reading from file (id128_read() and id128_read_fd()).
+                                 *
+                                 * This format should be used when reading a machine-id file. */
         ID128_UUID,   /* formatted as 36 character uuid string */
         _ID128_FORMAT_MAX,
 } Id128Format;