diff --git a/dbus/dbus-string.h b/dbus/dbus-string.h
index 95a03099..adf709bd 100644
--- a/dbus/dbus-string.h
+++ b/dbus/dbus-string.h
@@ -151,6 +151,22 @@ DBUS_PRIVATE_EXPORT
 int           _dbus_string_get_length            (const DBusString  *str);
 #endif /* !_dbus_string_get_length */
 
+/**
+ * Get the string's length as an unsigned integer, for comparison with
+ * size_t and similar unsigned types that does not trigger compiler
+ * warnings about potential value changes during conversion.
+ *
+ * DBusString lengths are signed for historical reasons, but we know that
+ * the length is always >= 0 (and DBUS_GENERIC_STRING_PREAMBLE asserts
+ * that this is the case) so we know that this cast does not change the
+ * value.
+ */
+static inline unsigned int
+_dbus_string_get_length_uint (const DBusString *str)
+{
+  return (unsigned int) _dbus_string_get_length (str);
+}
+
 DBUS_PRIVATE_EXPORT
 dbus_bool_t   _dbus_string_lengthen              (DBusString        *str,
                                                   int                additional_length);
diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
index 0bcd5abd..c7069521 100644
--- a/dbus/dbus-sysdeps-unix.c
+++ b/dbus/dbus-sysdeps-unix.c
@@ -1689,7 +1689,7 @@ add_linux_security_label_to_credentials (int              client_fd,
       _dbus_verbose ("getsockopt failed with %s, len now %lu\n",
                      _dbus_strerror (e), (unsigned long) len);
 
-      if (e != ERANGE || len <= _dbus_string_get_length (&buf))
+      if (e != ERANGE || len <= _dbus_string_get_length_uint (&buf))
         {
           _dbus_verbose ("Failed to getsockopt(SO_PEERSEC): %s\n",
                          _dbus_strerror (e));
@@ -1714,10 +1714,10 @@ add_linux_security_label_to_credentials (int              client_fd,
       goto out;
     }
 
-  if (len > _dbus_string_get_length (&buf))
+  if (len > _dbus_string_get_length_uint (&buf))
     {
-      _dbus_verbose ("%lu > %d", (unsigned long) len,
-                     _dbus_string_get_length (&buf));
+      _dbus_verbose ("%lu > %u", (unsigned long) len,
+                     _dbus_string_get_length_uint (&buf));
       _dbus_assert_not_reached ("getsockopt(SO_PEERSEC) overflowed");
     }