diff --git a/src/basic/string-util.c b/src/basic/string-util.c
index 2aac588118..c1e7e6e622 100644
--- a/src/basic/string-util.c
+++ b/src/basic/string-util.c
@@ -620,6 +620,9 @@ char *cellescape(char *buf, size_t len, const char *s) {
 char* strshorten(char *s, size_t l) {
         assert(s);
 
+        if (l >= SIZE_MAX-1) /* Would not change anything */
+                return s;
+
         if (strnlen(s, l+1) > l)
                 s[l] = 0;
 
diff --git a/src/test/test-string-util.c b/src/test/test-string-util.c
index e78e299ed2..92f1083a4c 100644
--- a/src/test/test-string-util.c
+++ b/src/test/test-string-util.c
@@ -299,8 +299,13 @@ TEST(ascii_strlower) {
 TEST(strshorten) {
         char s[] = "foobar";
 
+        assert_se(strlen(strshorten(s, SIZE_MAX)) == 6);
+        assert_se(strlen(strshorten(s, SIZE_MAX-1)) == 6);
+        assert_se(strlen(strshorten(s, SIZE_MAX-2)) == 6);
         assert_se(strlen(strshorten(s, 6)) == 6);
+        assert_se(strlen(strshorten(s, 7)) == 6);
         assert_se(strlen(strshorten(s, 12)) == 6);
+        assert_se(strlen(strshorten(s, 5)) == 5);
         assert_se(strlen(strshorten(s, 2)) == 2);
         assert_se(strlen(strshorten(s, 0)) == 0);
 }