diff --git a/src/basic/missing.h b/src/basic/missing.h
index e714078f31..dbdbd6f260 100644
--- a/src/basic/missing.h
+++ b/src/basic/missing.h
@@ -1407,4 +1407,11 @@ struct statx {
 #define AT_STATX_DONT_SYNC 0x4000
 #endif
 
+/* The maximum thread/process name length including trailing NUL byte. This mimics the kernel definition of the same
+ * name, which we need in userspace at various places but is not defined in userspace currently, neither under this
+ * name nor any other. */
+#ifndef TASK_COMM_LEN
+#define TASK_COMM_LEN 16
+#endif
+
 #include "missing_syscall.h"
diff --git a/src/basic/process-util.c b/src/basic/process-util.c
index a503aa50dc..058f077de0 100644
--- a/src/basic/process-util.c
+++ b/src/basic/process-util.c
@@ -296,7 +296,7 @@ int rename_process(const char name[]) {
          * can use PR_SET_NAME, which sets the thread name for the calling thread. */
         if (prctl(PR_SET_NAME, name) < 0)
                 log_debug_errno(errno, "PR_SET_NAME failed: %m");
-        if (l > 15) /* Linux process names can be 15 chars at max */
+        if (l >= TASK_COMM_LEN) /* Linux process names can be 15 chars at max */
                 truncated = true;
 
         /* Second step, change glibc's ID of the process name. */
diff --git a/src/test/test-process-util.c b/src/test/test-process-util.c
index fd5b44dc13..8b975ff988 100644
--- a/src/test/test-process-util.c
+++ b/src/test/test-process-util.c
@@ -366,7 +366,7 @@ static void test_rename_process_now(const char *p, int ret) {
 
         assert_se(get_process_comm(0, &comm) >= 0);
         log_info("comm = <%s>", comm);
-        assert_se(strneq(comm, p, 15));
+        assert_se(strneq(comm, p, TASK_COMM_LEN-1));
 
         assert_se(get_process_cmdline(0, 0, false, &cmdline) >= 0);
         /* we cannot expect cmdline to be renamed properly without privileges */