diff --git a/src/basic/string-util.c b/src/basic/string-util.c
index 5e4f57a5b1..b2919164d6 100644
--- a/src/basic/string-util.c
+++ b/src/basic/string-util.c
@@ -832,6 +832,8 @@ char* strextend_with_separator_internal(char **x, const char *separator, ...) {
                 t = va_arg(ap, const char *);
                 if (!t)
                         break;
+                if (t == POINTER_MAX)
+                        continue;
 
                 n = strlen(t);
 
@@ -864,6 +866,8 @@ char* strextend_with_separator_internal(char **x, const char *separator, ...) {
                 t = va_arg(ap, const char *);
                 if (!t)
                         break;
+                if (t == POINTER_MAX)
+                        continue;
 
                 if (need_separator && separator)
                         p = stpcpy(p, separator);
diff --git a/src/test/test-string-util.c b/src/test/test-string-util.c
index b692af6cc0..2b44905346 100644
--- a/src/test/test-string-util.c
+++ b/src/test/test-string-util.c
@@ -262,6 +262,12 @@ TEST(strextend) {
         ASSERT_STREQ(str, "0123");
         assert_se(strextend(&str, "456", "78", "9"));
         ASSERT_STREQ(str, "0123456789");
+
+        assert_se(strextend(&str, "more", NULL, "huch"));
+        ASSERT_STREQ(str, "0123456789more");
+
+        assert_se(strextend(&str, "MORE", POINTER_MAX, "HUCH"));
+        ASSERT_STREQ(str, "0123456789moreMOREHUCH");
 }
 
 TEST(strextend_with_separator) {
@@ -285,6 +291,9 @@ TEST(strextend_with_separator) {
         ASSERT_STREQ(str, "start,,1,234");
         assert_se(strextend_with_separator(&str, ";", "more", "5", "678"));
         ASSERT_STREQ(str, "start,,1,234;more;5;678");
+
+        assert_se(strextend_with_separator(&str, ";", "xxxx", POINTER_MAX, "yyy"));
+        ASSERT_STREQ(str, "start,,1,234;more;5;678;xxxx;yyy");
 }
 
 TEST(strrep) {
@@ -400,6 +409,10 @@ TEST(strjoin) {
         actual = strjoin("foo", NULL, "bar");
         ASSERT_STREQ(actual, "foo");
         free(actual);
+
+        actual = strjoin("foo", POINTER_MAX, "bar");
+        ASSERT_STREQ(actual, "foobar");
+        free(actual);
 }
 
 TEST(strcmp_ptr) {