diff --git a/fs/procfs/fs_procfsuptime.c b/fs/procfs/fs_procfsuptime.c
index fd92869bd17..12dd895b7e9 100644
--- a/fs/procfs/fs_procfsuptime.c
+++ b/fs/procfs/fs_procfsuptime.c
@@ -268,7 +268,7 @@ static ssize_t uptime_read(FAR struct file *filep, FAR char *buffer,
       /* Convert the seconds + hundredths of seconds to a string */
 
 #ifdef CONFIG_SYSTEM_TIME64
-      linesize = snprintf(attr->line, UPTIME_LINELEN, "%7llu.%02u\n",
+      linesize = snprintf(attr->line, UPTIME_LINELEN, "%7" PRIu64 ".%02u\n",
                           sec, csec);
 #else
       linesize = snprintf(attr->line, UPTIME_LINELEN, "%7lu.%02u\n",