diff --git a/apps/sbc/SBCCallProfile.cpp b/apps/sbc/SBCCallProfile.cpp
index 3885bcb6..58e9638e 100644
--- a/apps/sbc/SBCCallProfile.cpp
+++ b/apps/sbc/SBCCallProfile.cpp
@@ -234,6 +234,7 @@ bool SBCCallProfile::readFromConfiguration(const string& name,
     CP_SST_CFGVAR("", "maximum_timer", sst_b_cfg);
     CP_SST_CFGVAR("", "session_refresh_method", sst_b_cfg);
     CP_SST_CFGVAR("", "accept_501_reply", sst_b_cfg);
+    CP_SST_CFGVAR("", "sst_strict_mode", sst_b_cfg);
   }
 
   if (sst_aleg_enabled.size() && sst_aleg_enabled != "no") {
@@ -244,6 +245,7 @@ bool SBCCallProfile::readFromConfiguration(const string& name,
     CP_SST_CFGVAR("aleg_", "maximum_timer", sst_a_cfg);
     CP_SST_CFGVAR("aleg_", "session_refresh_method", sst_a_cfg);
     CP_SST_CFGVAR("aleg_", "accept_501_reply", sst_a_cfg);
+    CP_SST_CFGVAR("aleg_", "sst_strict_mode", sst_a_cfg);
   }
 #undef CP_SST_CFGVAR
 
@@ -553,6 +555,8 @@ bool SBCCallProfile::readFromConfiguration(const string& name,
 	   sst_a_cfg.getParameter("session_refresh_method").c_str());
       INFO("SBC:              accept_501_reply=%s\n",
 	   sst_a_cfg.getParameter("accept_501_reply").c_str());
+      INFO("SBC:              sst_strict_mode=%s\n",
+	   sst_a_cfg.getParameter("sst_strict_mode").c_str());
     }
     INFO("SBC:      SST on B leg enabled: '%s'\n", sst_enabled.empty() ?
 	 "no" : sst_enabled.c_str());
@@ -567,6 +571,8 @@ bool SBCCallProfile::readFromConfiguration(const string& name,
 	   sst_b_cfg.getParameter("session_refresh_method").c_str());
       INFO("SBC:              accept_501_reply=%s\n",
 	   sst_b_cfg.getParameter("accept_501_reply").c_str());
+      INFO("SBC:              sst_strict_mode=%s\n",
+	   sst_b_cfg.getParameter("sst_strict_mode").c_str());
     }
 
     INFO("SBC:      SIP auth %sabled\n", auth_enabled?"en":"dis");
@@ -776,6 +782,7 @@ void SBCCallProfile::eval_sst_config(ParamReplacerCtx& ctx,
     "maximum_timer",
     "session_refresh_method",
     "accept_501_reply",
+    "sst_strict_mode",
   };
 
   for(unsigned int i=0; i<SST_CFG_PARAM_COUNT; i++) {
diff --git a/apps/sbc/etc/auth_b2b.sbcprofile.conf b/apps/sbc/etc/auth_b2b.sbcprofile.conf
index 848eb9b7..4f010c5e 100644
--- a/apps/sbc/etc/auth_b2b.sbcprofile.conf
+++ b/apps/sbc/etc/auth_b2b.sbcprofile.conf
@@ -57,6 +57,7 @@ message_filter=transparent
 #minimum_timer=90
 #session_refresh_method=UPDATE_FALLBACK_INVITE
 #accept_501_reply=yes
+#sst_strict_mode=yes
 
 #################################################################
 #This profile implements a pure B2BUA application that does an
diff --git a/apps/sbc/etc/sbc.conf b/apps/sbc/etc/sbc.conf
index 033df47d..e67ca8f6 100644
--- a/apps/sbc/etc/sbc.conf
+++ b/apps/sbc/etc/sbc.conf
@@ -69,3 +69,9 @@ active_profile=transparent
 #
 #accept_501_reply=no
 
+# sst_strict_mode - disable session timers for a leg if an INVITE/UPDATE
+# request or a positive response does not declare "Supported: timer".
+#
+# Default: yes
+#
+#sst_strict_mode=no
diff --git a/apps/sbc/etc/sst_b2b.sbcprofile.conf b/apps/sbc/etc/sst_b2b.sbcprofile.conf
index 16522ac0..9bab8475 100644
--- a/apps/sbc/etc/sst_b2b.sbcprofile.conf
+++ b/apps/sbc/etc/sst_b2b.sbcprofile.conf
@@ -49,6 +49,7 @@ enable_session_timer=yes
 #maximum_timer=900
 #session_refresh_method=UPDATE_FALLBACK_INVITE
 #accept_501_reply=yes
+#sst_strict_mode=yes
 
 #separate SST configuration for A (caller) leg:
 #enable_aleg_session_timer=$H(P-Enable-A-SST)
@@ -57,6 +58,7 @@ enable_session_timer=yes
 #aleg_maximum_timer=900
 #aleg_session_refresh_method=UPDATE_FALLBACK_INVITE
 #aleg_accept_501_reply=yes
+#aleg_sst_strict_mode=yes
 
 #
 #This application can be routed through for achieving 
diff --git a/apps/sbc/etc/transparent.sbcprofile.conf b/apps/sbc/etc/transparent.sbcprofile.conf
index c2692aeb..19ef088f 100644
--- a/apps/sbc/etc/transparent.sbcprofile.conf
+++ b/apps/sbc/etc/transparent.sbcprofile.conf
@@ -114,6 +114,7 @@
 #minimum_timer=90
 #session_refresh_method=UPDATE_FALLBACK_INVITE
 #accept_501_reply=yes
+#sst_strict_mode=yes
 
 ##separate SST configuration for A (caller) leg, optional:
 #enable_aleg_session_timer=yes
@@ -122,6 +123,7 @@
 #aleg_maximum_timer=900
 #aleg_session_refresh_method=UPDATE_FALLBACK_INVITE
 #aleg_accept_501_reply=yes
+#aleg_sst_strict_mode=yes
 
 ## refuse call
 # refuse all calls with <code> <reason>
diff --git a/core/plug-in/session_timer/SessionTimer.cpp b/core/plug-in/session_timer/SessionTimer.cpp
index 6eae4d2c..6ed4431f 100644
--- a/core/plug-in/session_timer/SessionTimer.cpp
+++ b/core/plug-in/session_timer/SessionTimer.cpp
@@ -269,8 +269,8 @@ void SessionTimer::updateTimer(AmSession* s, const AmSipRequest& req) {
     remote_timer_aware = key_in_list(getHeader(req.hdrs, SIP_HDR_SUPPORTED, SIP_HDR_SUPPORTED_COMPACT),
                                       TIMER_OPTION_TAG);
 
-    /* disable timers for this leg if not declare explicitly (UPDATE only) */
-    if (req.method == SIP_METH_UPDATE && !remote_timer_aware) {
+    /* disable timers for this leg if not declare explicitly */
+    if (session_timer_conf.StrictMode && !remote_timer_aware) {
       /* timer is not supported by originator's leg */
       DBG("Session timer not supported by request originator's leg, remove session timer intervals");
       session_timer_conf.setEnableSessionTimer(false);
@@ -369,7 +369,7 @@ void SessionTimer::updateTimer(AmSession* s, const AmSipReply& reply)
   remote_timer_aware = key_in_list(getHeader(reply.hdrs, SIP_HDR_SUPPORTED, SIP_HDR_SUPPORTED_COMPACT),
                                     TIMER_OPTION_TAG);
 
-  if (!remote_timer_aware) {
+  if (session_timer_conf.StrictMode && !remote_timer_aware) {
     /* timer is not supported by responder's leg */
     DBG("Session timer not supported by responder's leg, remove session timer intervals");
     session_timer_conf.setEnableSessionTimer(false);
@@ -483,7 +483,8 @@ AmSessionTimerConfig::AmSessionTimerConfig()
   : EnableSessionTimer(DEFAULT_ENABLE_SESSION_TIMER), 
     SessionExpires(SESSION_EXPIRES), 
     MinimumTimer(MINIMUM_TIMER),
-    MaximumTimer(MAXIMUM_TIMER)
+    MaximumTimer(MAXIMUM_TIMER),
+    StrictMode(false)
 {
 }
 
@@ -528,6 +529,21 @@ int AmSessionTimerConfig::readFromConfig(AmConfigReader& cfg)
     MaximumTimer = (unsigned int) maximum_timer;
   }
 
+  /* SST strict mode allows to re-init timers during the session,
+   * whenever remote side with INVITE/UPDATE method doesn't
+   * declare `Supported: timer` explicitly. By default always: no.
+   */
+  if(cfg.hasParameter("sst_strict_mode")){
+    if (cfg.getParameter("sst_strict_mode", "no") == "yes") {
+      DBG("SST strict mode is enabled by profile settings (default: no).\n");
+      StrictMode = true;
+    }
+    else {
+      DBG("SST strict mode is disabled by profile settings (default: no).\n");
+      StrictMode = false;
+    }
+  }
+
   return 0;
 }
 
diff --git a/core/plug-in/session_timer/SessionTimer.h b/core/plug-in/session_timer/SessionTimer.h
index 20822040..ace01fa4 100644
--- a/core/plug-in/session_timer/SessionTimer.h
+++ b/core/plug-in/session_timer/SessionTimer.h
@@ -85,7 +85,8 @@ class AmSessionTimerConfig
 public:
   AmSessionTimerConfig();
   ~AmSessionTimerConfig();
-  
+
+  bool StrictMode;
 
   /** Session Timer: Enable Session Timer?
       returns 0 on invalid value */