1 files changed, 10 insertions, 0 deletions
diff --git a/src/modules/m_spanningtree.cpp b/src/modules/m_spanningtree.cpp
index 8e7fb4264..f2137e1d0 100644
--- a/src/modules/m_spanningtree.cpp
+++ b/src/modules/m_spanningtree.cpp
@@ -1878,6 +1878,11 @@ class TreeSocket : public InspSocket
 				{
 					return this->Capab(params);
 				}
+				else if ((command == "U") || (command == "S"))
+				{
+					this->WriteLine("ERROR :Cannot use the old-style mesh linking protocol with m_spanningtree.so!");
+					return false;
+				}
 				else
 				{
 					this->WriteLine("ERROR :Invalid command in negotiation phase.");
@@ -1893,6 +1898,11 @@ class TreeSocket : public InspSocket
 					// silently ignore.
 					return true;
 				}
+				else if ((command == "U") || (command == "S"))
+				{
+					this->WriteLine("ERROR :Cannot use the old-style mesh linking protocol with m_spanningtree.so!");
+					return false;
+				}
 				else if (command == "BURST")
 				{
 					this->LinkState = CONNECTED;