--- snmplib/snmpusm.c.orig    2016-08-10 11:42:17.000000000 +0500
+++ snmplib/snmpusm.c 2016-08-10 11:46:34.000000000 +0500
@@ -2213,7 +2213,7 @@
          * XXX  Contrary to the pseudocode:
          *      See if boots is invalid first.
          */
-        if (theirBoots == ENGINEBOOT_MAX || theirBoots > boots_uint) {
+        if (theirBoots == ENGINEBOOT_MAX) {
             DEBUGMSGTL(("usm", "%s\n", "Remote boot count invalid."));
 
             *error = SNMPERR_USM_NOTINTIMEWINDOW;
@@ -2223,20 +2223,11 @@
 
         /*
          * Boots is ok, see if the boots is the same but the time
-         * is old.
+         * is acceptable old.
          */
-        if (theirBoots == boots_uint && time_uint < theirLastTime) {
-            if (time_difference > USM_TIME_WINDOW) {
-                DEBUGMSGTL(("usm", "%s\n", "Message too old."));
-                *error = SNMPERR_USM_NOTINTIMEWINDOW;
-                return -1;
-            }
-
-            else {              /* Old, but acceptable */
-
-                *error = SNMPERR_SUCCESS;
-                return 0;
-            }
+        if (theirBoots == boots_uint && time_uint < theirLastTime && time_difference < USM_TIME_WINDOW) {
+            *error = SNMPERR_SUCCESS;
+            return 0;
         }