if (len + strlen(last_elem) + 2 > PATH_MAX)
                                die ("Too long path name: '%s/%s'",
                                                buf, last_elem);
-                       buf[len] = '/';
-                       strcpy(buf + len + 1, last_elem);
+                       if (len && buf[len-1] != '/')
+                               buf[len++] = '/';
+                       strcpy(buf + len, last_elem);
                        free(last_elem);
                        last_elem = NULL;
                }