diff --git a/core/AmConfig.cpp b/core/AmConfig.cpp
index 472a1358..cf2a33bc 100644
--- a/core/AmConfig.cpp
+++ b/core/AmConfig.cpp
@@ -107,6 +107,7 @@ bool         AmConfig::LogEvents               = false;
 int          AmConfig::UnhandledReplyLoglevel  = 0;
 
 bool         AmConfig::SkipGenerateDirectionBoth = false;
+bool         AmConfig::IgnoreRouteSetOnPrack     = false;
 
 #ifdef WITH_ZRTP
 bool         AmConfig::enable_zrtp             = true;
@@ -412,6 +413,10 @@ int AmConfig::readConfiguration()
     SkipGenerateDirectionBoth = (cfg.getParameter("skip_generate_direction_both") == "yes");
   }
 
+  if(cfg.hasParameter("ignore_routeset_on_prack")) {
+    IgnoreRouteSetOnPrack = (cfg.getParameter("ignore_routeset_on_prack") == "yes");
+  }
+
   if(cfg.hasParameter("sip_nat_handling")) {
     SipNATHandling = (cfg.getParameter("sip_nat_handling") == "yes");
   }
diff --git a/core/AmConfig.h b/core/AmConfig.h
index b32e97f0..58c63bc4 100644
--- a/core/AmConfig.h
+++ b/core/AmConfig.h
@@ -207,6 +207,11 @@ struct AmConfig
   static vector <string> CodecOrder;
 
   static bool SkipGenerateDirectionBoth;
+  /** strict RFC 3261 behavior for the 200 OK on PRACK: when true, the route
+   *  set is not updated (it is taken once when the dialog is created) and the
+   *  remote tag is only taken from the 200 OK on PRACK if it was not yet set.
+   *  false (default) keeps the legacy behavior of updating both. */
+  static bool IgnoreRouteSetOnPrack;
 
   enum ApplicationSelector {
     App_RURIUSER,
diff --git a/core/AmSipDialog.cpp b/core/AmSipDialog.cpp
index 82b9933d..3979da4e 100644
--- a/core/AmSipDialog.cpp
+++ b/core/AmSipDialog.cpp
@@ -598,14 +598,26 @@ bool AmSipDialog::onRxReplyStatus(const AmSipReply& reply)
   /* PRACK */
   } else if (reply.cseq_method == SIP_METH_PRACK) {
     /* do not update call leg status for transactions not involving INVITE.
-     * In this case just update the to-tag and route set */
-    if (!reply.to_tag.empty()) {
-      ILOG_DLG(L_DBG, "Updating remote tag (to tag) to: '%s'.\n", reply.to_tag.c_str());
-      setRemoteTag(reply.to_tag);
-    }
-    if (!reply.route.empty()) {
-      ILOG_DLG(L_DBG, "Updating route set to: '%s'.\n", reply.route.c_str());
-      setRouteSet(reply.route);
+     * With ignore_routeset_on_prack=yes the route set is taken once when the
+     * dialog is created and is not updated by the 200 OK on PRACK; the remote
+     * tag is still taken from the 200 OK on PRACK only if it was not already
+     * known. The default (no) keeps the legacy behavior of updating both from
+     * the 200 OK on PRACK.
+     */
+    if (AmConfig::IgnoreRouteSetOnPrack) {
+      if (!reply.to_tag.empty() && getRemoteTag().empty()) {
+        ILOG_DLG(L_DBG, "Taking remote tag (to tag) from PRACK 200 OK: '%s'.\n", reply.to_tag.c_str());
+        setRemoteTag(reply.to_tag);
+      }
+    } else {
+      if (!reply.to_tag.empty()) {
+        ILOG_DLG(L_DBG, "Updating remote tag (to tag) to: '%s'.\n", reply.to_tag.c_str());
+        setRemoteTag(reply.to_tag);
+      }
+      if (!reply.route.empty()) {
+        ILOG_DLG(L_DBG, "Updating route set to: '%s'.\n", reply.route.c_str());
+        setRouteSet(reply.route);
+      }
     }
   }
 
diff --git a/core/etc/sems.conf.cmake b/core/etc/sems.conf.cmake
index fbd165de..f241faec 100644
--- a/core/etc/sems.conf.cmake
+++ b/core/etc/sems.conf.cmake
@@ -426,6 +426,18 @@ use_default_signature=yes
 #
 #100rel=require
 
+# ignore the route set from the 200 OK on PRACK? [yes, no]
+#
+# yes  - strict RFC 3261: the route set is taken once when the dialog is
+#        created and not updated, and the remote tag is taken from the 200 OK
+#        on PRACK only if it was not already known.
+# no   - legacy behavior: the route set and remote tag are updated from the
+#        200 OK on PRACK.
+#
+# Default: no
+#
+#ignore_routeset_on_prack=yes
+
 # Make SIP authenticated requests sticky to the proxy? [yes | no]
 #
 # If enabled, host of request-URI of out-of-dialog requests that are
diff --git a/core/etc/sems.conf.sample b/core/etc/sems.conf.sample
index 354d744a..4bcd5847 100644
--- a/core/etc/sems.conf.sample
+++ b/core/etc/sems.conf.sample
@@ -576,6 +576,18 @@ use_default_signature=yes
 #
 #100rel=require
 
+# ignore the route set from the 200 OK on PRACK? [yes, no]
+#
+# yes  - strict RFC 3261: the route set is taken once when the dialog is
+#        created and not updated, and the remote tag is taken from the 200 OK
+#        on PRACK only if it was not already known.
+# no   - legacy behavior: the route set and remote tag are updated from the
+#        200 OK on PRACK.
+#
+# Default: no
+#
+#ignore_routeset_on_prack=yes
+
 # force the use of outbound interface? [yes, no]
 #
 # Useful in case of overlapping networks, or if OS routing can/should not be used.