diff --git a/src/basic/in-addr-util.c b/src/basic/in-addr-util.c
index 39ae694f20..6bf017260b 100644
--- a/src/basic/in-addr-util.c
+++ b/src/basic/in-addr-util.c
@@ -460,15 +460,12 @@ int in_addr_prefix_to_string(int family, const union in_addr_union *u, unsigned
         assert(ret);
 
         if (family == AF_INET)
-                l = INET_ADDRSTRLEN + 3;
+                l = INET_ADDRSTRLEN + 1 + DECIMAL_STR_MAX(unsigned);
         else if (family == AF_INET6)
-                l = INET6_ADDRSTRLEN + 4;
+                l = INET6_ADDRSTRLEN + 1 + DECIMAL_STR_MAX(unsigned);
         else
                 return -EAFNOSUPPORT;
 
-        if (prefixlen > FAMILY_ADDRESS_SIZE(family) * 8)
-                return -EINVAL;
-
         x = new(char, l);
         if (!x)
                 return -ENOMEM;
diff --git a/src/test/test-in-addr-prefix-util.c b/src/test/test-in-addr-prefix-util.c
index 6503353465..d2991b9d3d 100644
--- a/src/test/test-in-addr-prefix-util.c
+++ b/src/test/test-in-addr-prefix-util.c
@@ -3,6 +3,29 @@
 #include "in-addr-prefix-util.h"
 #include "tests.h"
 
+static void test_in_addr_prefix_to_string_one(int f, const char *addr, unsigned prefixlen) {
+        union in_addr_union ua;
+        _cleanup_free_ char *r;
+
+        assert_se(in_addr_from_string(f, addr, &ua) >= 0);
+        assert_se(in_addr_prefix_to_string(f, &ua, prefixlen, &r) >= 0);
+        printf("%s: %s/%u == %s\n", __func__, addr, prefixlen, r);
+        assert_se(startswith(r, addr));
+}
+
+TEST(in_addr_to_string_prefix) {
+        test_in_addr_prefix_to_string_one(AF_INET, "192.168.0.1", 0);
+        test_in_addr_prefix_to_string_one(AF_INET, "192.168.0.1", 1);
+        test_in_addr_prefix_to_string_one(AF_INET, "192.168.0.1", 31);
+        test_in_addr_prefix_to_string_one(AF_INET, "192.168.0.1", 32);
+        test_in_addr_prefix_to_string_one(AF_INET, "192.168.0.1", 256);
+        test_in_addr_prefix_to_string_one(AF_INET, "10.11.12.13", UINT_MAX);
+        test_in_addr_prefix_to_string_one(AF_INET6, "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff", 0);
+        test_in_addr_prefix_to_string_one(AF_INET6, "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff", UINT_MAX);
+        test_in_addr_prefix_to_string_one(AF_INET6, "::1", 11);
+        test_in_addr_prefix_to_string_one(AF_INET6, "fe80::", 33);
+}
+
 static void test_config_parse_in_addr_prefixes_one(int family, const union in_addr_union *addr, uint8_t prefixlen, Set **prefixes) {
         _cleanup_free_ char *str = NULL;
 
diff --git a/src/test/test-in-addr-util.c b/src/test/test-in-addr-util.c
index c0808d51b9..296cd27434 100644
--- a/src/test/test-in-addr-util.c
+++ b/src/test/test-in-addr-util.c
@@ -351,7 +351,7 @@ static void test_in_addr_to_string_one(int f, const char *addr) {
 
         assert_se(in_addr_from_string(f, addr, &ua) >= 0);
         assert_se(in_addr_to_string(f, &ua, &r) >= 0);
-        printf("test_in_addr_to_string_one: %s == %s\n", addr, r);
+        printf("%s: %s == %s\n", __func__, addr, r);
         assert_se(streq(addr, r));
 
         assert_se(streq(r, IN_ADDR_TO_STRING(f, &ua)));