diff --git a/src/nm-initrd-generator/nmi-cmdline-reader.c b/src/nm-initrd-generator/nmi-cmdline-reader.c
index 59b9f04b1f..ba5380afb2 100644
--- a/src/nm-initrd-generator/nmi-cmdline-reader.c
+++ b/src/nm-initrd-generator/nmi-cmdline-reader.c
@@ -544,7 +544,7 @@ reader_parse_ip(Reader *reader, const char *sysfs_dir, char *argument)
     NMSettingConnection           *s_con;
     NMSettingIPConfig             *s_ip4 = NULL, *s_ip6 = NULL;
     gs_unref_hashtable GHashTable *ibft = NULL;
-    const char                    *tmp;
+    char                          *tmp;
     const char                    *tmp2;
     const char                    *tmp3;
     const char                    *kind;
@@ -589,15 +589,25 @@ reader_parse_ip(Reader *reader, const char *sysfs_dir, char *argument)
             kind       = tmp3;
         } else {
             /* <client-IP>:[<peer>]:<gateway-IP>:<netmask>:<client_hostname>:<kind> */
-            client_ip = tmp;
+
+            /* note: split here address and prefix to normalize IPs defined as
+             * [dead::beef]/64. Latter parsing would fail due to the '[]'. */
+            client_ip = get_word(&tmp, '/');
+
             if (client_ip) {
-                client_ip_family = get_ip_address_family(client_ip, TRUE);
+                client_ip_family = get_ip_address_family(client_ip, FALSE);
                 if (client_ip_family == AF_UNSPEC) {
                     _LOGW(LOGD_CORE, "Invalid IP address '%s'.", client_ip);
                     return;
                 }
             }
 
+            if (!nm_str_is_empty(tmp)) {
+                gboolean is_ipv4 = client_ip_family == AF_INET;
+
+                client_ip_prefix = _nm_utils_ascii_str_to_int64(tmp, 10, 0, is_ipv4 ? 32 : 128, -1);
+            }
+
             peer            = tmp2;
             gateway_ip      = get_word(&argument, ':');
             netmask         = get_word(&argument, ':');
@@ -672,11 +682,7 @@ reader_parse_ip(Reader *reader, const char *sysfs_dir, char *argument)
         NMIPAddress *address = NULL;
         NMIPAddr     addr;
 
-        if (nm_inet_parse_with_prefix_bin(client_ip_family,
-                                          client_ip,
-                                          NULL,
-                                          &addr,
-                                          client_ip_prefix == -1 ? &client_ip_prefix : NULL)) {
+        if (nm_inet_parse_bin(client_ip_family, client_ip, NULL, &addr)) {
             if (client_ip_prefix == -1) {
                 switch (client_ip_family) {
                 case AF_INET:
diff --git a/src/nm-initrd-generator/tests/test-cmdline-reader.c b/src/nm-initrd-generator/tests/test-cmdline-reader.c
index af13849c8c..cd7b1069b6 100644
--- a/src/nm-initrd-generator/tests/test-cmdline-reader.c
+++ b/src/nm-initrd-generator/tests/test-cmdline-reader.c
@@ -597,7 +597,7 @@ static void
 test_if_ip6_manual(void)
 {
     gs_unref_hashtable GHashTable *connections = NULL;
-    const char *const             *ARGV = NM_MAKE_STRV("ip=[2001:0db8::02]/64::[2001:0db8::01]::"
+    const char *const             *ARGV = NM_MAKE_STRV("ip=[2001:0db8::02]/56::[2001:0db8::01]::"
                                                        "hostname0.example.com:eth4::[2001:0db8::53]");
     NMConnection                  *connection;
     NMSettingIPConfig             *s_ip4;
@@ -633,7 +633,7 @@ test_if_ip6_manual(void)
     ip_addr = nm_setting_ip_config_get_address(s_ip6, 0);
     g_assert(ip_addr);
     g_assert_cmpstr(nm_ip_address_get_address(ip_addr), ==, "2001:db8::2");
-    g_assert_cmpint(nm_ip_address_get_prefix(ip_addr), ==, 64);
+    g_assert_cmpint(nm_ip_address_get_prefix(ip_addr), ==, 56);
     g_assert_cmpstr(nm_setting_ip_config_get_gateway(s_ip6), ==, "2001:db8::1");
     g_assert_cmpstr(nm_setting_ip_config_get_dhcp_hostname(s_ip6), ==, NULL);
 }