diff --git a/src/libsystemd/sd-id128/id128-util.c b/src/libsystemd/sd-id128/id128-util.c
index 9ffd594ee6..985872b82d 100644
--- a/src/libsystemd/sd-id128/id128-util.c
+++ b/src/libsystemd/sd-id128/id128-util.c
@@ -11,7 +11,7 @@
 #include "io-util.h"
 #include "stdio-util.h"
 
-char *id128_to_uuid_string(sd_id128_t id, char s[37]) {
+char *id128_to_uuid_string(sd_id128_t id, char s[static ID128_UUID_STRING_MAX]) {
         unsigned n, k = 0;
 
         assert(s);
diff --git a/src/libsystemd/sd-id128/id128-util.h b/src/libsystemd/sd-id128/id128-util.h
index 82a69a77f3..fe0149a8aa 100644
--- a/src/libsystemd/sd-id128/id128-util.h
+++ b/src/libsystemd/sd-id128/id128-util.h
@@ -8,7 +8,9 @@
 #include "hash-funcs.h"
 #include "macro.h"
 
-char *id128_to_uuid_string(sd_id128_t id, char s[37]);
+#define ID128_UUID_STRING_MAX 37
+
+char *id128_to_uuid_string(sd_id128_t id, char s[static ID128_UUID_STRING_MAX]);
 
 bool id128_is_valid(const char *s) _pure_;
 
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 9fac326219..d1ad8a37c8 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -2866,7 +2866,7 @@ static int inner_child(
                 FDSet *fds) {
 
         _cleanup_free_ char *home = NULL;
-        char as_uuid[37];
+        char as_uuid[ID128_UUID_STRING_MAX];
         size_t n_env = 1;
         const char *envp[] = {
                 "PATH=" DEFAULT_PATH_COMPAT,
diff --git a/src/shared/logs-show.c b/src/shared/logs-show.c
index 95b2e3376e..27b8ccd5e4 100644
--- a/src/shared/logs-show.c
+++ b/src/shared/logs-show.c
@@ -17,6 +17,7 @@
 #include "format-util.h"
 #include "hashmap.h"
 #include "hostname-util.h"
+#include "id128-util.h"
 #include "io-util.h"
 #include "journal-internal.h"
 #include "json.h"
@@ -26,8 +27,8 @@
 #include "namespace-util.h"
 #include "output-mode.h"
 #include "parse-util.h"
-#include "process-util.h"
 #include "pretty-print.h"
+#include "process-util.h"
 #include "sparse-endian.h"
 #include "stdio-util.h"
 #include "string-table.h"
@@ -1353,8 +1354,8 @@ int add_matches_for_user_unit(sd_journal *j, const char *unit, uid_t uid) {
 static int get_boot_id_for_machine(const char *machine, sd_id128_t *boot_id) {
         _cleanup_close_pair_ int pair[2] = { -1, -1 };
         _cleanup_close_ int pidnsfd = -1, mntnsfd = -1, rootfd = -1;
+        char buf[ID128_UUID_STRING_MAX];
         pid_t pid, child;
-        char buf[37];
         ssize_t k;
         int r;
 
diff --git a/src/test/test-id128.c b/src/test/test-id128.c
index 4d7513f6d5..66eedddce8 100644
--- a/src/test/test-id128.c
+++ b/src/test/test-id128.c
@@ -21,7 +21,7 @@
 
 int main(int argc, char *argv[]) {
         sd_id128_t id, id2;
-        char t[33], q[37];
+        char t[SD_ID128_STRING_MAX], q[ID128_UUID_STRING_MAX];
         _cleanup_free_ char *b = NULL;
         _cleanup_close_ int fd = -1;
         int r;
diff --git a/src/veritysetup/veritysetup-generator.c b/src/veritysetup/veritysetup-generator.c
index f2b74f3dc1..ea1d056600 100644
--- a/src/veritysetup/veritysetup-generator.c
+++ b/src/veritysetup/veritysetup-generator.c
@@ -166,7 +166,7 @@ static int parse_proc_cmdline_item(const char *key, const char *value, void *dat
 static int determine_devices(void) {
         _cleanup_free_ void *m = NULL;
         sd_id128_t root_uuid, verity_uuid;
-        char ids[37];
+        char ids[ID128_UUID_STRING_MAX];
         size_t l;
         int r;