diff --git a/src/journal/journald-kmsg.c b/src/journal/journald-kmsg.c
index 4123fda5f92..95135decaa4 100644
--- a/src/journal/journald-kmsg.c
+++ b/src/journal/journald-kmsg.c
@@ -258,11 +258,9 @@ void dev_kmsg_record(Server *s, char *p, size_t l) {
         iovec[n++] = IOVEC_MAKE_STRING(source_boot_time);
 
         /* Historically, we stored the timestamp 'usec' as _SOURCE_MONOTONIC_TIMESTAMP, so we cannot remove
-         * the field as it is already used in other projects. So, let's store the correct timestamp here by
-         * mapping the boottime to monotonic. Then, the existence of _SOURCE_BOOTTIME_TIMESTAMP indicates
-         * the reliability of _SOURCE_MONOTONIC_TIMESTAMP field. */
+         * the field as it is already used in other projects. This is for backward compatibility. */
         char source_monotonic_time[STRLEN("_SOURCE_MONOTONIC_TIMESTAMP=") + DECIMAL_STR_MAX(unsigned long long)];
-        xsprintf(source_monotonic_time, "_SOURCE_MONOTONIC_TIMESTAMP="USEC_FMT, map_clock_usec(usec, CLOCK_BOOTTIME, CLOCK_MONOTONIC));
+        xsprintf(source_monotonic_time, "_SOURCE_MONOTONIC_TIMESTAMP=%llu", usec);
         iovec[n++] = IOVEC_MAKE_STRING(source_monotonic_time);
 
         iovec[n++] = IOVEC_MAKE_STRING("_TRANSPORT=kernel");