diff --git a/shared/nm-glib-aux/nm-shared-utils.h b/shared/nm-glib-aux/nm-shared-utils.h
index abe263c6bd..2d4054f7c2 100644
--- a/shared/nm-glib-aux/nm-shared-utils.h
+++ b/shared/nm-glib-aux/nm-shared-utils.h
@@ -183,13 +183,13 @@ nm_utils_inet_ntop (int addr_family, gconstpointer addr, char *dst)
 }
 
 static inline const char *
-_nm_utils_inet4_ntop (in_addr_t addr, char *dst)
+_nm_utils_inet4_ntop (in_addr_t addr, char dst[static INET_ADDRSTRLEN])
 {
 	return nm_utils_inet_ntop (AF_INET, &addr, dst);
 }
 
 static inline const char *
-_nm_utils_inet6_ntop (const struct in6_addr *addr, char *dst)
+_nm_utils_inet6_ntop (const struct in6_addr *addr, char dst[static INET6_ADDRSTRLEN])
 {
 	return nm_utils_inet_ntop (AF_INET6, addr, dst);
 }
diff --git a/src/nm-core-utils.c b/src/nm-core-utils.c
index 03dbbcf81f..cbbac2816b 100644
--- a/src/nm-core-utils.c
+++ b/src/nm-core-utils.c
@@ -2999,7 +2999,8 @@ nm_utils_ipv6_interface_identifier_get_from_token (NMUtilsIPv6IfaceId *iid,
  * Returns: the input buffer filled with the id as string.
  */
 const char *
-nm_utils_inet6_interface_identifier_to_token (NMUtilsIPv6IfaceId iid, char *buf)
+nm_utils_inet6_interface_identifier_to_token (NMUtilsIPv6IfaceId iid,
+                                              char buf[static INET6_ADDRSTRLEN])
 {
 	struct in6_addr i6_token = { .s6_addr = { 0, } };
 
diff --git a/src/nm-core-utils.h b/src/nm-core-utils.h
index 7d63d06afc..fbb7987573 100644
--- a/src/nm-core-utils.h
+++ b/src/nm-core-utils.h
@@ -316,7 +316,7 @@ gboolean nm_utils_ipv6_interface_identifier_get_from_token (NMUtilsIPv6IfaceId *
                                                            const char *token);
 
 const char *nm_utils_inet6_interface_identifier_to_token (NMUtilsIPv6IfaceId iid,
-                                                         char *buf);
+                                                          char buf[static INET6_ADDRSTRLEN]);
 
 gboolean nm_utils_get_ipv6_interface_identifier (NMLinkType link_type,
                                                  const guint8 *hwaddr,