strlcpy(boot_command_line, arcs_cmdline, COMMAND_LINE_SIZE);
 
        if (EXTEND_WITH_PROM && arcs_cmdline[0]) {
-               strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
+               if (boot_command_line[0])
+                       strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
                strlcat(boot_command_line, arcs_cmdline, COMMAND_LINE_SIZE);
        }
 
 #if defined(CONFIG_CMDLINE_BOOL)
        if (builtin_cmdline[0]) {
-               strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
+               if (boot_command_line[0])
+                       strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
                strlcat(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
        }
 #endif