diff --git a/src/core/ngx_parse.c b/src/core/ngx_parse.c
index d7350d423..7b60c5fb6 100644
--- a/src/core/ngx_parse.c
+++ b/src/core/ngx_parse.c
@@ -188,7 +188,7 @@ ngx_parse_time(ngx_str_t *line, ngx_uint_t is_sec)
             break;
 
         case 'm':
-            if (*p == 's') {
+            if (p < last && *p == 's') {
                 if (is_sec || step >= st_msec) {
                     return NGX_ERROR;
                 }